I've studied Kaizo mods and levels for the past year or so, and I can say with absolute certainty, this isn't one of the good ones I've played.
The level design is hard as nails, yes, but it's not really Kaizo. It's mostly spam of the obstacles and enemies of the game, and it hardly does anything particularly creative with them. At later points, it just gets ridiculous with how it expects even the best players to go through obstacles that require nearly pixel perfect precision. I refuse to believe this was properly playtested, especially not the bosses or special stages.
It feels like you're intended to do this with infinite lives, but no, you don't even get continues. Locking the player out of their save after getting a game over is just plain cheap. And I know you can just play it in Multiplayer with lives set to infinite, but I think that's a flimsy excuse for objectively miserable design.
Nearly every good Kaizo mod either disables lives altogether, or at least lets you continue, so you don't have to endlessly limp through the same miserable stages you just spent hours grinding, just to retry the level you were stuck on before.
This mod can absolutely do better. I hope you do improve this, because a good Kaizo for SRB2 has the potential to be amazing. This mod, however, doesn't capitalize on it.
As for improving this mod without completely re-making it by re-imagining the levels(and thus changing lvl geometry alot), what I'm getting from your review is that I need to vary the environmental hazards more(possibly in very large part by taking more liberties with thematics), letting players have infinite lives, not removing starposts from the later stages, and probably revising enemy placements and the new enemy mechanics too.
Plus, you can barely call the enemy part spam; I didn't even add many extra enemies to each level(except RVZ).
That said, I'd planned to improve this mod anyway, but I don't have anything in mind yet aside from being more lenient with lives & continues, which I didn't have in mind before reading this review.