I don't think Wyll is unpopular because he has so little content - I mean, people love Minthara who also does not have much - but because he is a terrible moraliser while at the same time being shown as a not very skilled monster hunter. Leftovers of his old plot, I guess. Personally, I also bench him often because he is still picking fights in the most stupid manner when everyone else has started to get along.
A scene that also bothers me in regards to the second point, is the scene of him and Karlach in Avernus, during which he is given the completely silent role of a Tav who needs the Hells explained to them. Considering how the story for him and Karlach starts, that doesn't feel ok and undermines his monster hunter status once more. I haven't checked if the scene is voiced now, though, admittedly.
Not my opinion, but that is ok. I only know of one person, he picks fights with, and that is perfectly in character for him imo.
Minthara like Halsin has been made a companion because of fan demand, so it was clear, she is popular (evil drow woman is a must have since Viconia I guess). Halsin has even less content, but was also a fan demand.
