When even stock rocket in KSP2 says NO to orbit!

well... the game is a mess,that´s true...
but your decoupling-skill is even worse,and that means something ;)

"insanity is the practice of doing the same thing over and over again while expecting things to change"

Cut the engine. Separate. Full Throttle.

Sir, this is why sepatrons exist

Just use seperatrons smhhh

Try seperating the solid bosters right befor they run out so they get to fly off

you probably have too much AoA