What Lights said is not wrong. It seems you are starting to take her advice seeing your more recent plays but I guess I should clarify just in case. Right after this post you set these scores:
To say the least, its not pretty but could be worse. I'm going to give you the benefit of the doubt, and assume you were playing multiplayer or something. Once in a while its OK to set scores like these. However it will greatly stunt your improvement. Now I really need you to listen to me, or you can just completely ignore my advice. I just don't want you to get stuck in the same pointless wall as me.
I looked through some of those replays, and although you're hitting the notes your accuracy is abominable. It could be worse though: at least you played a variety of maps without spamming retry hoping for a better score. However its important for you to try a map at least a few times as it takes repetition to form muscle memory. Later on you played a bunch of 2* and scored high accuracy, but it didn't look like it took much effort. Perhaps you were bored and just wanted to pass some songs, but this is also not going generate improvement.
Take a look at this graph:
It outlines the steps that your brain takes to learn something new. As you can see there's a lot to it, but the most important parts are closer down to the middle. When you play a new pattern only once or twice, you only get through the first few levels, which don't really form any neural connections. You need to see and play the pattern several times before your brain can get close to recognizing how to process it and understand it.
In that sense, its perfectly OK to play hard maps. When building muscle, many people swear by progressive overloading, the idea that you should always push yourself harder than you did last week in order to avoid plateauing. Mania is a bit different though, as unlike pure body building there's a lot of technique which takes time to perfect. Getting high accuracy is critical to improvement as it shows you actually understand what your playing vs. just hitting keys at approximately the right time.
My recommendation for your improvement from here on out is to go back to those high 2* and slowly work your way up to high 3*, playing songs 2-5 times until you get at least an S. If you can't get the S, try playing a different map of a similar level, don't spam retry. Once your able to S most high 3*, you can probably beat a lot of easier 4*. Mania is kind of broken in that sense.
Feel free to play super hard maps or PP maps from time to time. It's fun. But always keep in mind what Lights said, because if you lose track of what you can and can't play you'll end up like me, setting lucky high star low acc scores once a few months and getting demotivated for the rest of the year. Don't end up like that. Good luck, feel free to PM so that you can figure out exactly what you don't want to do.