This touches on the "everybody else in the discipline" aspect I have been thinking about lately; my conclusion is that we have a spectrum of inclusive to exclusive sports.
Think about snooker: to live off it you need to be really good, as in train for 8+ hours a day, every day. The top player will earn multiples of 250k GBP a year, but already a 3rd ranker will at best do a "decent office job". Everybody else pays to play. This is an exclusive sport.
But look at UTMB[1]: A guy having a day job and training a couple of hours before and after work... was able to finish it under 100 hours, which is jaw-dropping. This is an inclusive sport.
Now pro boxing: you can't have a ranking without enough contenders, and by definition there can only be one champion at a time. So you have the champion, contenders, gatekeepers, journeyman and... everybody else is the filler. It's an inclusive sport, but by pure statistics most players will be filler.
1: https://en.wikipedia.org/wiki/Ultra-Trail_du_Mont-Blanc