The environments in this expansion are good, the new monster designs are neat, the dungeons and trials and solo duties have been fine. The gameplay overall is the same gameplay from Endwalker with a few new buttons, people saying the gameplay is so much more amazing are huffing petrol from the can (Don't be rama rama).
The plot is definitely the weakest link of this expansion so far. Part of that is Endwalker resolved plotlines introduced in 2.0 (maybe even 1.0, I dunno about that mess) and then introduced an even bigger cosmic threat. Going from beating the big bad evil guy who had been around in the background through the base game and four expansions to "Hey this dopey chick needs help with becoming ruler of Brazil or something lol" is an enormous letdown for players. While one may feel the need to excuse this with "Well, they painted themselves into a corner" or some other platitude, shit is still shit, and this de-escalation of stakes is shit.
Wuk Lamat is emblematic of this in many ways, and I think her introduction to the MSQ was botched. Her arrival was made worse due to heralding this de-escalation. She just pops up with little warning and an attitude from the writers that we should adore her unquestioningly. Her introduction presents her as a very stereotypical character common in Japanese media, and were this a manga and I was the editor, I would send her back to be redesigned for lack of depth. She lacks any real nuance to make her worthy of interest. She is overshadowed by her own backstory. While I could recommend other ways they could have framed her introduction to ameliorate both her lack of depth and the de-escalation of the plot, who fucking cares because what is done is done. This is the turd sandwich we have been served, and it is up to us to either eat it or walk away.