Being unable to maximize a specific character's potential is pretty far from where you said "there are certain important ways in which you simply cannot progress without spending money."

There's nothing in the main content that requires you to have a 5* character/weapon, even though it's certainly easier with them.

Hm? I'm super-lazy game mechanic wise. I spend money. But 3 of the chacters on my team are free, and I almost never use combos because I can't be bothered to do complex stuff. I'm sure I don't maximize my damage-per-second but I still enjoy the game and defeating nearly all enemies is completely doable even with casual gaming skills.

If the critique is "I can't maximize to the absolute highest stats without paying" -- then sorry, I think that's an attitude full of false entitlement.

Heck, look at this frickin video about how they produced the Liyue OST: https://youtu.be/pFrKZxStL_U They commissioned a massive Shanghai orchestra team to produce excellent music. And we get all this amazing stuff for free.

> But the core mechanic is swapping between different characters for combos and synergies.

The game gives you a free character of each element to handle the necessary synergies.

There's a difference between "severely hampered" and less effective at end-game content.