In what way does experience count in the game?

Would it just be progression of attributes, particularly mental attributes?

If you are referring to players, "decisions" and possibly "consistency" are attributes I can think of that generally rise with experience.

As for what else does experience affect, I am not too sure. Perhaps a propensity for higher wages as a player ages?

If you are referring to players, "decisions" and possibly "consistency" are attributes I can think of that generally rise with experience.

As for what else does experience affect, I am not too sure. Perhaps a propensity for higher wages as a player ages?

Yes, I was referring to players.

Various hidden attributes. Experienced players are less likely to lose morale quickly when you are on a losing streak (dependent on their personality traits too of course) and that kind of thing.

I'd say yes. Experience, if you can call it that, only influence attributes, not performance. As players get older and play more games mental attributes (hidden and visible) will rise, and in some way you can call that experience. But if you have two identically skilled players, one who's 30 years with 500 games behind him and one who's 20 with 50 games, they will be equal IMO.