In my experience as someone who is down to pug/mix but is a washed middie at best, most of the 'popular' places to pug that are created eventually become the same circlejerks of Top Mid to D1 players who all know one another and generally result in quite cringy pugs in general. Even these new sites just feels like PugChamp 2, with all the same upsides and downsides.
Someone said it best early on, most pugging groups start fairly accessible but over time more and more players join and it then just becomes another one of these circlejerk groups. I can only think of like two groups of in-houses I've played in where the matches have been good, even actually enjoyable, and both of them are fairly tightknit groups and not a openly public method of pugging.
Just having more players pugging is not the solution, its about having a system where people of all skill levels can find a group or community around their level where they can actually play competitive. Whether thats a formal matchmaking system like faceit, multiple smaller community pugging sites like tf2pickup, simple in-houses, or a mixture of all three. In all honesty, I'd actually be down for some more div-locked pug groups/site but I feel that in practice they would either a) suck and/or b) be dead af.