I don't think there has ever been a pug platform that has had the infrastructure to support a decent amount of pugs without having dogshit quality pugs because of the picking system(faceit). If these issues were addressed, I don't think player count would be an issue.
Most people were happy with the pugchamp system of picking, it's just that pugs never happened for a decent proportion of the playerbase since there were never enough medics, and of those medics, they were usually playing far above the level they deserved to be at due to that same shortage of medics/better meds playing combat classes instead. But I think that random medics has become enough of a standard that bringing back that system with a random medic feature would be a good solution.
Like literally just have pugchamp, but you don't need medics/captains (or an admin to get a server and do rcon shit) to start a pug. Then the system randomizes meds out of those added who then captain for their teams. Medics should usually be fine skill level wise since ppl who add are expecting to get picked which means they are roughly good enough for the pug. Maybe have some kind of opt in/out for the pug if you don't think you'll get picked and don't want to get rolled on med. Make it so that ppl can only get rolled once a day and it resets at 3 AM or something.
I get what tasheem is saying about circlejerks and stuff, but honestly pughub is about as public as it gets for a pug group, and styles pugs' only barrier is skill level.