Sure :) Advancing past 1500 requires more than just avoiding blunders - it requires positional understanding, more complex tactics, and above all consistency. This becomes especially important for longer time controls if you play over-the-board, because a single mistake can be fatal. Thus, reaching 2000-2200 requires deeper understanding of the game, which is best obtained by reading the right books and analysing your long games. Blitz chess, on the other hand, teaches a lot of bad habits. It teaches you to play against the opponent's clock, rather than the opponent's position; for example, it is best to play a dubious move in blitz if it creates a complicated position when your opponent is low on time. It also teaches that speed is more important than consistency; conserving time more important than accurate moves. It also teaches you to look for cheap tactics, like forks and skewers, since your opponent is less likely to spot them with less time. None of these practices will translate to better Rapid or OTB standard performance. I'm not saying Blitz isn't fun - I find it quite exciting (in moderation!). But as an improvement tool, you will quickly hit a brick wall with it. As any coach or top player will tell you, they got there through hard work and systematic training, and not through Blitz.
It depends on the person
Here are a few ways blitz can be helpful
1.competitivness blitz is naturally more competitive due to more titled players and otb players playing it and the pressure it gives
2.it does actually teach you positional play which is more important than "thinking well" stockfish is all calculation but it sucks why is that ? Because you need to see and endgame /know what positions you need to reach you learn that by playing my games not just by "analyzing "
3.tempo it teaches you how to make forcing moves in a relatively balanced time management
4.humans don't really have the attention span to pay attention for 3 min much less calculate for 15
That's why chess requires obsesivness you can't really pay attention for that long unless you enjoy it
5.yes rapid is better if you don't know the fundamentals but once you know the fundamentals any time control is good just analyze your games after usually people figure out the fundamentals between 1200-1600 elo
6.depends some people do worse in blitz others in rapid
Example of you have tunnel vision rapid unless it is irl otb might not be the best idea cause you will just come out/in and not pay attention then flag blitz prevents that it does not give you time to zone out rather zoning in is helpful cause you keep a solid tempo
To improve at chess, you have to learn to think... Playing chess so fast that you hardly have time to move the pieces will not help with that!
Actually I do better in classical I have outplayed ims in rapid quite a few times
I'm primarily a blitz player
Rapid I don't have enough time to think so speed chess is helpful more time isn't always good when trying to learn something sometimes pressure is super helpful but it depends on the person