My answer is that I don't have access to what I'd really like to base that judgment upon: their success rate, adjusted for the difficulty of the procedure.

Simpler, less-risky procedures would therefore have a lower skill/experience bar.

Basically, I'd want someone with decades of experiences to remove a tumor deep inside my brain, but I'd be much more willing to use someone who learned via YouTube this time last year if I'd suffered a TBI and was experiencing swelling and intra-cranial pressure.

No unnecessary gatekeeping, but maximum necessary quality standards (which I distinguish from gatekeeping).