Your first point has almost no correlation to anything else in your post. I'm not really sure why you included it. It's a server/connection issue, and as far as I know not intentionally abusable.

I disagree with "True" combos being bad. Is it frustrating to be hit by a longer one? Yeah, totally. But it's not much different than you mistiming your first dodge and being beat up for a bit because of it. You're basically advocating for hitstun to be shorter, which is a terrible idea.

360 hitboxes can be pretty frustrating, yeah. In my experience, however, they are nowhere near good enough to be an actual problem. They have windups, or long recovery periods, or short range, or any other reason that makes them easily punishable, for the most part.

I don't really know specifically what you mean by "gimp", but if you miss a dodge, you should be punished - especially at your elo. If they're going to "spike" you (whatever that might mean) and you miss the dodge, of course they'll follow it up with another one. Though even without dodges you can still avoid things, just jump away (not always possible, but still a viable alternative.) Or hit them first.

I don't know if I agree with your assessment of why Hattori is bad. If you play a low-def high-speed legend, you should be expected to avoid things. On the other end of the spectrum, Nai/Roland can be abused by faster champions and are almost required to "trade blows" in order to win. For faster, flimsier legends - yeah, you probably need more overall game knowledge. That doesn't mean they require more skill, though.

As to kb vs controller, the debate has been brought up hundreds of times on this sub alone. Just search for the threads about it. They almost always end up saying "it's down to preference" and "neither has a clear advantage."

As far as I can tell, the main thing you seem to think players "abuse" is using strings (trues as well as not) to damage you. Unfortunately, if you think combos in a fighting game like this is "abusing" a game mechanic, then Brawlhalla is not the game for you.