If you’re including all non-experienced shooters
Even if you include only gun owners that think they're experienced, it's still easy-ish to be better than average with focused practice. There are a lot of people that think going to the range once every six months and shooting 100 rounds of slow fire makes them good. Meanwhile, the people that are actually good do dryfire drills daily, and shoot thousands of rounds each month.
I'm solidly low-middle when it comes to shooting competitions like local PCSL, local USPSA, Brutality, Gun Run, etc. That probably puts me in the top 5% of gun owners though. (And I absolutely suck at long range shooting; I've done a little, but I don't know my holds, because I've had very limited ability to shoot past 100y. I really struggle past 300y without a spotter, and past 500y it's basically pure luck for me to hit a full-sized steel IPSC target.)