It’s true that many gymnasts tend to be smaller, but there are ample examples of “average sized” (or greater) calisthenics athletes who achieve planches and whatnot. I don’t have numbers or sources on hand but they are often referred to as the strongest “pound for pound” athletes. As
@xagunos correctly stated, that type of training requires meticulous planning, consistency and most of all PATIENCE. For those reasons I think it’s actually really hard to compare body weight/calisthenics to barbell/weight training. I don’t view one as better than the other; they’re just different. Most people just want to know they are getting stronger, and weights provide that. Progress in calisthenics can be sloooooowwwww..... which can be disheartening.