I feel like it's a lot of things that keeps a C player a C player. I hear it said a lot that it has to do with mentality, but that's a really broad category. But I think I'll just rant a bit:
They don't plan ahead. On an open and run-able table, they don't plan the next shot, and just keep shooting until they run out of things to shoot. They don't solve problems, and you can see it in their eyes. They see a ball that can goes in a pocket, they shoot it, and look for another open ball. I think their brains are just wired to not believe a run-out is even a possibility, so they just keep pocketing balls until they.
Another one that kills me, is I see players try to emulate what they consider to be better players (who are usually just lifetime C-players who have been playing longer) but without any of the understanding. On a wide open table, they just start banging in balls like they run 8 balls every day. They'll move quick from shot to shot, like it's natural, but nothing they've ever done prior, would suggest that they can run 8 balls naturally.
Shapes a mess, and they pretend that that's where they intended for the cue-ball to go all along. I hate when a player just pounds the cue-ball, and it luckily is somehow getting shape on a random ball they didn't choose, and they wave it in like they're helping someone back up a truck. When I started my first league I bought me and my league partner laser pointers, so that we could literally point to the area we wanted the cue-ball to go. I was getting so frustrated because here I am trying to learn how to play position and being godawful, and he's waving his truck in. Having him point at the area he wanted at least got him to clue in on how awful he was, so that we could be awful together.
I think some people are just naturally gifted and have an instinct for the game, but even so, at some point or another, you need to do the research to understand how pool works (physics etc). I think a lot of C-players are the culmination of years of experience. They've naturally learned and figured out everything they know by themselves without any outside information. The everyday example of what a man can accomplish with just himself and a pool table, and it sucks.
Sorry if this was mean, it just bugs me so much. I'm new to pool, but I work hard at it, and I'm just at the point, where I can safely expect to run-out at least once a night. And I can feel the local players that I'm trying to learn from sucking me down. They are my mentors because they were better than me 6 months ago. Their advice now, seems terrible. They'll wonder why I made a tougher shot, when there was an easy shot (usually a hanger). Here I am trying to break out a problem ball, and I ask them when it's correct to solve it, and they don't even have a plan for it. They say they'll worry about it later, and 6 balls later, it's still a problem. I get their logic though, from the perspective of trying to score as many points as possible because it's league (1 pt per ball). So I understand trying to get as many points as you can, And there's been a few times where I look stupid cause I'm trying to fix all my problems instead of putting down object balls and I'll lose like 10-3, but I think forgoing the short term advantages is important. I need to think like a player who is going to run-out consistently even if I can't at the moment.
I think there's just a complete difference between a lifetime C-player, and a temporary C-player. The way they think about the game is just completely different from start to finish. It's not a quick fix, and I never realized that it was such a huge difference until I started writing this.
Rant Over