Under Armor just doesn’t have “cool” factor. Their gear is top notch outside of their shoes. While Nike and Adidas were busy fighting over deals with teams and leagues, UA tried to get the biggest athletes. Arguable they succeeded in their strategy: Tom Brady, Steph Curry, Bryce Harper, Cam Newton, Jordan Spieth, etc. but without the backing of a major league, and minimal top tier colleges they never gained traction with the public. UA was supposed take over MLBs uniforms instead of Nike, but they had to back out because they were going bankrupt.
Most gear these days is bought and sold based solely on clout. Nike has the most clout, adidas second, UA third, then everybody else is fighting for the rest. It’s a shame really, I miss when there was more competition so the big brands had to make higher quality merchandise. I still think Russel Athletic makes some of the highest quality gear. Everybody just thinks it’s lame so it’s automatically lame. If you took the uniforms and and gear that Russel made/makes and put a swoosh on it, everybody would probably love it. Obviously there were some stinkers on their design front, but every company has those. The materials and the feel of the gear itself from Russel is just as good if not better than the big brands.