I am currently running clipless on my mountain bike and it is a great setup for longer distances and not too technical climbs. Where I find they lack is when I’m trying to go over an obstacle. I’m scared to fully commit knowing I may get stuck and not be able to unclip fast enough to bail. I also think clipless allows you to cheat a bit and pull up on your pedals instead of properly maneuvering over things. A few of my friends have switched back to flats.
But...nothing beats clipless when you are cruisssssing on a fire road or flowy trails.