That depends on the game I think. Games like Battlefield have no problem with players of all skills playing the same match - some are trying hard, some are chiling out, some are doing something silly, either way the scene is so large you can usually choose what you like the best, it all organizes itself naturally. BR games like PUBG always have very different players in one high-ish level match (as it's not possible to pick that many players of a matching skill) and that's completely fine.

Games and leagues where you're expected to try hard are entirely different. I'd say custom tiered PUG queues are much better than common huge pools, this way top players can filter people they're training and playing with. In the end I think I rather agree with the grandparent than not, communities typically feel more lively and diverse than blind ladders.