A character doesn't need to have the spotlight on them 100% of the time to be the main character. Other characters also need to be developed and that means putting the spotlight on them occasionally. As long as the main character takes part in the development of the other characters, they haven't lost their position as main character.
Was it wrong to put a spotlight on Wuk Lamat this expansion? No, since the first half of the story was about her attempt to win the throne and the second half about her attempts to protect her people after getting the throne and learning of a threat. The WoL was still very present with an integral role in the story arc. The WoL still remains the main character for the game.
The problem with the story was they mishandled Wuk Lamat's character development. They created a Mary Sue, realized they had created a Mary Sue, decide to slap on some poorly chosen random flaws so she wouldn't seem like a Mary Sue (still didn't work) and then had most of those flaws disappear, reappear and disappear again for no logical reason. Even worse to me, they gave her a medical condition then used it only as a way to mock the character instead of as something that could have been used in her character development.
I see people point at the voice acting for the character but the voice acting was actually well done considering what they were given to work with - a badly written character with some rather cringy dialog at times.
As others have said, more should have been done to flesh out Wuk's character development instead of making that development mirror Wuk Evu's behavior ("oh I've done wrong how terrible of me" "it was fine, forget it" "okay, forgotten").
The MSQ really should have been 2 separate stories - a 7.0 MSQ developing Wuk's character with the WoL's assistance, then 7.1-?.? where the WoL is brought back to Tural to help investigate the Alexandria mystery. Shoving them together into one story did neither part justice. It was the same mistake made with Endwalker's story but at least that had almost a decade of backstory to lean on. This one needed to be able to stand on its own but end up doing a lot of wobbling for lack of support.