I am nowhere near you score, but I have heard many strong players stating that blitz is bad for you, and actually creates bad habits for classical.
Ultimately, though, what this world championship proves is that we need to get rid of the distinction between "classical" and "blitz". The "classical" world championship was just decided by a few games of rapid.
Fundamentally, the question is how to get good at "chess" - thinking fast and slow. Over-training at any one time control will weaken you in the others. But will increase your overall strength.
Some players (myself included, 2400 bullet and 2250 classical) probably need to spend more time training and playing classical than bullet. The vast majority of players I encounter are much weaker in blitz than in classical, including many IMs and GMs. For these people I would prescribe a few thousand games of bullet chess, fix 'em up right quick.
Interesting point. Competitive coding has virtually nothing to do with real world software engineering. But, since it's still coding, you could learn a lot of bad habits from doing it that might carry over into the real world. Better to get into <competitive hobby> instead.
I'm terrible, terrible at chess, but at least I don't hang my queen or do other truly stupid shit in longer time controls. You can't even really start to play chess for real until you stop just giving up pieces and I think as long as you're throwing games that hard, I dunno if rapid/blitz is the best place for you.
Or at least, that's what I think you might have heard when you say you've heard "blitz is bad for you". Once you stop doing the truly stupid shit, then you can start learning chess for real, and maybe then it's better to do rapid/blitz.
I know in Starcraft2 there was a component of grinding that pros would recommend, but you can't really grind if you don't know how to do screen hotkeys, for example.
Most people struggle to get good at chess because they are too afraid to lose, and too afraid to actually do the "practice" part of playing which is to analyze your losses to identify which areas you need to train.
Grinding is not how you get better. Grinding can be fun, and can be a great way to blow off steam. Both of those are awesome reasons to play chess. But if you are serious about improving quickly, do what the pros do. Don't grind aimlessly. Play a lot, don't be afraid to lose, and do legit post-mortems to give you feedback on where you need to pay more attention.