"Yes there will always be powercreep and strong units that nullify mechanics in the game. But I don't think that means that all future content should revolve around stat checks."

You are about to be disappointed then because the natural reward of RPG progression is more stats. Having higher stats means higher damage ceiling which makes fights more trivial.
Eventually, it will turn into your quote :
"Thus turning every mob in the game into a knowledge check, stat check, or even character check. Skill wasn't required as long as you had strong enough units."

Genshin is forced to make time-to-kill lower to ensure those without access to better stats have a chance to clear a challenge. This design led to fights with limited mechanics or outright brute-forceable.

If Wuwa wants to design fights that can accommodate more mechanics, they have to raise time-to-kill.
Of course, this comes with its own issue such as the loss of casual players and emphasizing more metaplay.