I would say most XC FS bikes that are competitive are going to be in the 25lb range or lower. Trailbikes tend to average from 27lb-32lb depending on how much you spend. Enduro rigs will be one or two lbs heavier than that.
As for whether it matters a lot, it really depends on how you ride and what you relative comparisons are. When I had a 30lb FS bike and a 23lb hardtail, the FS bike felt like my brakes were rubbing all the time or I was dragging a bowling ball around. Not fun. But when I was on a long vacation and rented a 30lb enduro rig, I got used to it after a couple days and didn’t notice the weight after that. So I would say if you only have one rig, it probably will not matter too much unless you race. But if you have a light rig and a heavy one, my guess is you will slowly stop riding the heavy one unless you are doing lift assisted riding.