As we all know, there is a rule that the lowest difficulty should be under 2.0 stars. And the purpose of this rule is to provide a difficulty that a newbie can enjoy - thus it implies that the lowest difficulty should be beginner-friendly. I'm pretty sure that regular Normal diffs are not pretty much playable for starters, and I saw that some BNs think that it should just be an Easy diff.

However, lowest difficulties are still a beatmap, which should represent a reasonable amount of beats in the music that can show the uniqueness of that specific music. We don't want a map which only represents the big white ticks for the entire map. In most cases, it is possible to avoid monotony and provide some various rhythms while still being beginner-friendly. But there are cases that cannot achieve both.

First case is when the song is extremely fast. Assume that there is a 270bpm song with full of 1/2 beats. To make an Easy difficulty out of this song, the map should mostly contain 2/1 beats and 4/1 beats only. This means it's missing more than 3 important sounds while it is representing only 1 of them. And this will mostly cause the notes to be on very very basic ticks, which are important in any kind of songs, thus it doesn't represent the uniqueness of the song at all.

Another case is when the song has very tricky rhythms. Most common example of this is when the song is constructed with many anacrusises. We usually don't want that in Easy diffs because it's hard to perceive the beat transition. However, there is no way to avoid it when the song is just like that. If the song is fast, this becomes even worse. If we want to avoid those "polarity issues", the only way is to use like 1 note per measure, which is really dumb. Oh we can also try to use reverse sliders or use different combination of circles/sliders just to avoid this one issue, but we know that it vitally restricts constructing patterns and providing proper emphasis.

Some songs simply don't call for a beginner-friendly diff imo. If we just only care about the minimum rule "SR < 2.0", it's fine in 99.99% cases. But if we start to think about "beginner-friendly" things, we have to see maps that can be hardly said to be "following the music". So, how should be interpret this rule? Do we want to anyway provide an beginner-friendly diff no matter how it accurately follows the music? Or is it fine to have a Normal diff as the lowest diff that maximally simplified the rhythms just enough to represent the very essence of the song?

Uhmm I kinda think you've got two small detail wrong here, the point you seem to argue about is not the 2*-rule but the guideline saying "If your mapset does not have an Easy difficulty your Normal difficulty should follow the general guidelines for Easy difficulties", and this guideline doesn't say that it should be beginner-friendly but that it should follow the Easy-guidelines (-> not using snaps smaller than 1/1 etc.). So that kinda resolves this whole issue for me, I see zero reason to force a low-*-diff onto a fast or tricky song for all those reasons you already explained, and it's not demanded by the RC either.

If it's a very technical song, it's just a smarter mapping decision to stop at a Normal since mapping an Easy usually ends up skipping certain notes.

However, you seem to be implying that if a song is very technical, that mappers shouldn't map an Easy/Beginner/etc... I think that's just unnecessary. The mapper should be able create easy difficulties, even for hard songs. Just because a difficulty is unnecessary for the spread doesn't mean it needs to be discarded. If it doesn't follow the song well because of the rhythms chosen, that's the mapper's fault for using poor rhythm choice, and you should try to recommend rhythms that fit the difficulty better.

In any case though, im like 95% sure that the majority of ppl who play "Easy/Beginner" diffs use at least 3 mods to play them anyways. To me, Easy's and other maps are created for clean spreads, and less because they want to include the 5 or so beginners who actually need to play a difficulty that low xD.

Okay, let me clarify my points.

Right above that SR < 2.0 rule, there's another rule

The mapset must have a well-designed spread of difficulties, containing at least an Easy or a Normal difficulty. This is so that players of all levels of experience are able to enjoy maps of the songs they love.

So we want players of all levels of experience to be able to enjoy. If a beginner cannot enjoy any of the difficulties, it's not a set for the players of all levels of experience. That's why I also interpret the SR < 2.0 rule as they should be beginner-friendly. If it's not for that, why would we have that rule at all.

Does that clarify my points? So it's like "We need a difficulty that even a beginner can play, as the rule says" -> "it requires too much simplification to make a map beginner-friendly, when the song is too fast or has tricky rhythms" -> "Do we still want at least one beginner-friendly difficulty in all cases?"

Anyway as we discussed on Discord it's hard to clarify as a rule or anything, so probably we just should leave it to each cases I suppose...

Plans are as follows: define what the lowest difficulties for each mode may use to be beginner-friendly enough and then get rid of an arbitrary limit based on an SR algorithm which could be changed in the future.

That's why the difficulty specific Ranking Criteria sections are a thing for osu! and osu!catch for now and why drafts for these in Taiko and osu!mania will follow, just so we have difficulty levels for each gamemode defined and can get rid of SR as part of the Ranking Criteria without creating ambiguity.

All that is probably necessary is to amend an addition to all of these drafts that define "when is it ok to omit an Easy and when do you need one" as separate case-specific rules and guidelines.

Doyak wrote:

As we all know, there is a rule that the lowest difficulty should be under 2.0 stars. And the purpose of this rule is to provide a difficulty that a newbie can enjoy - thus it implies that the lowest difficulty should be beginner-friendly. I'm pretty sure that regular Normal diffs are not pretty much playable for starters, and I saw that some BNs think that it should just be an Easy diff.

While I see where are you going, I don't find the rule itself implies it should or needs to be beginner-friendly. The rule says that you have at least one difficulty for the better players and one for the 'not-so-good-players'. While it's a set concept that Normal is an "easier" difficulty this sort of difficulty is enough to make a mapset rankable, spread-wise. The two things "Normal" and "beginner-friendly" cannot harmonize, the limit of 2.0 stars is just a hard limit - like the minimum of drain time a map needs to have to be rankable/approvable.

Doyak wrote:

Some songs simply don't call for a beginner-friendly diff imo. If we just only care about the minimum rule "SR < 2.0", it's fine in 99.99% cases. But if we start to think about "beginner-friendly" things, we have to see maps that can be hardly said to be "following the music". So, how should be interpret this rule? Do we want to anyway provide an beginner-friendly diff no matter how it accurately follows the music? Or is it fine to have a Normal diff as the lowest diff that maximally simplified the rhythms just enough to represent the very essence of the song?

I agree with you at the point that some Normal difficulties treaten as the lowest difficulty aren't beginner-friendly, however I think we cannot always ensure that every ranked mapset with a somewhat existing spread is beginner-friendly. It's always great if you have not only a Normal and Hard difficulty but also an Easy one. But try to force that, especially for longer songs.

Doyak wrote:

Right above that SR < 2.0 rule, there's another rule

The mapset must have a well-designed spread of difficulties, containing at least an Easy or a Normal difficulty. This is so that players of all levels of experience are able to enjoy maps of the songs they love.

So we want players of all levels of experience to be able to enjoy. If a beginner cannot enjoy any of the difficulties, it's not a set for the players of all levels of experience. That's why I also interpret the SR < 2.0 rule as they should be beginner-friendly. If it's not for that, why would we have that rule at all.

Does that clarify my points? So it's like "We need a difficulty that even a beginner can play, as the rule says" -> "it requires too much simplification to make a map beginner-friendly, when the song is too fast or has tricky rhythms" -> "Do we still want at least one beginner-friendly difficulty in all cases?"

I am unsure HOW picky we are for the descriptions of each rule but I mean you're right that N/H mapsets do not meet that requirement of being a set for all levels of experience. That would also mean that players mainly playing Insanes are affected by that. But I am still unsure how exactly we should go with the description..