Used to dislike the idea of FL, but lately it actually feels like a cool mod; Here is why
Just imagine it, fast forward to the future in your osu playtime, in many many plays from now you're a player like azuraer, who can S (or SS) any map on his first try. Every week there's about 30~ new maps that are worth playing, you S all of them in like 2 hours, now what? What if you played osu a little on thursday and on friday, and then felt like playing a little more on saturday... but you've already S'd every single map worth playing. Now what?
Playing old maps again normally would be boring, and not everybody likes to grind for SS; so at this point, the challenge of trying to memorize a map you like as fast as possible can actually be interesting, because you'll pretty much be stuck playing only maps you already passed anyway, so why not add a new challenge to it.
...but if somebody only uses FL to get a top score in the rankings it's p.lame
Just imagine it, fast forward to the future in your osu playtime, in many many plays from now you're a player like azuraer, who can S (or SS) any map on his first try. Every week there's about 30~ new maps that are worth playing, you S all of them in like 2 hours, now what? What if you played osu a little on thursday and on friday, and then felt like playing a little more on saturday... but you've already S'd every single map worth playing. Now what?
Playing old maps again normally would be boring, and not everybody likes to grind for SS; so at this point, the challenge of trying to memorize a map you like as fast as possible can actually be interesting, because you'll pretty much be stuck playing only maps you already passed anyway, so why not add a new challenge to it.
...but if somebody only uses FL to get a top score in the rankings it's p.lame