I hate the disparaging of gatekeeping as inherently bad. Mountain biking has seen an uptick of people riding electric fat bikes, essentially just dirt bikes. It’s bad enough when beginners are using normal bikes to ride in wet muddy conditions on trails that can’t handle it or skidding into corners, it does so much more damage when they’re tearing up the trail with a heavy motorized bike with wide tires. More gatekeeping would keep the trails in better conditions.
It also seems straight up dangerous, for themselves and others, at least on downhill trails. If they’re going down them, well, it’s already dangerous enough for beginners (who always seem to ignore the difficulty ratings) without adding extra speed. But the issue I’ve seen time and again is folks riding those things up the trails that people are actively trying to ride down. They were never designed with two-way traffic in mind, and going up it just chews it up even more.