Anything lift access can get overcrowded, but I've never felt overcrowded on a normal trail ride. I don't know about you guys, but on an average Fromme ride I rarely see more than like 20 riders after I leave the parking lot. Yes, on the prime weekends over the warmer months the top busy trails (bobsled, half nelson, espresso, boogie nights, lost lake, etc.) and shuttle routes might get a fair bit of traffic but it's easy to escape that just by riding different trails.
IMO the main trail networks have mostly been totally underutilized and still have a lot of room for additional capacity outside of a select few trails/routes.
According to trailforks Squamish has 588km of trails (I assume that's overstated and counts a lot of dirt roads and multi use paths, but say the real # is 1/3 of that (approx. 200km). Mathematically, you could have 2,000 riders riding at once and they would each have 100m of trail to themselves. Obviously that's not how it works in the real world, but I think you get what I am trying to say.
I think the issue is more around stuff like parking, where a bottleneck occurs.