In my experience the reason behind devs loving matchmaking is fairly straightforward: being able to solo queue raises engagement. It takes time and effort to make a team in the first place, more time and effort to coordinate games when you're now schedule wrangling n other people, and that extra effort is magnified across all the teams participating. In contrast, hopping into soloqueue is so brainless that the hours spent playing soloqueue end up dwarfing the hours spent playing as teams. Will some people who care enough still play team mode? Sure, but if solo matchmaking is an option it becomes the default simply through being the most-played mode. At the end of the day, devs seem rationally interested in juicing engagement numbers for the vast majority of the playerbase and letting those serious enough to care about not pugging figure it out for themselves.

I think there's a pretty limited space for games that don't compromise on various aspects of design (matchmaking, mtx, etc) with the explicit goal of making a better top-end competitive ecosystem. I'd personally love to see a competitive team-based game without any form of solo queue, but I'm skeptical it would do well in the market. It's almost like Facebook engagement-doomscrolling vs. a mailing list: the format of the latter means there'll probably be better content, but a whole lot more people are going to be hanging out on the former. At least mailing lists don't have to recoup development costs.