The WoL not being the MC is not a big deal, after all we are basically a mute character so since SE kinda wants for the WoL to be mostly an empty canvas for every player to project on it.

The main issue is that our WoL contribution is diminish to ridiculous levels to the point a random adventurer could do our job. Wuk Lamat literally bending the plot and becoming as powerful as the plot need her to be would be fine on a Manderville quest, not on the MSQ, as well as basically not growing at all as a character and everyone catering to her whims and praising her actions like if they were her personal bootlickers.

To that add a bad narrative pacing, padding and filler everywhere, non sensical plot and antagonists that make some Disney ones look Shakesperian and thats the reason why DT reception is mixed at best.

Heavensward is an example how how the MCs were Estinien, Ysaile and Alphinaud and you didnt feel like the WoL was some kind of decorative ornament, or how the narrative could be low stakes and dont be a sub par story, since Heavensward was confined to Ishgard alone, there wasnt some big stakes there and its considered one of the best expansions ever story wise