In terms of quality, no. So far each subsequent region has been more interesting to explore than the last one. I mean, compare Mondstadt, which is just one big boring green field, to Inazuma, where each island has a unique theme and story and music. Or compare early bosses like regisvines and cubes to wolf lord, even if just in terms of design. I would argue they even try to get better with storytelling (but fail miserably) - the premise of Inazuma story is so much more interesting than a dragon terrorizing a village, even if its execution failed.

I think the game will become better in some aspects and worse/more stale in others, but it definitely hasn't lost its ambition yet.