When it comes to skilled play, it seems to me that some questions to which existence proofs are relevant include:
1. Is it possible to have RPGing in which playing with skill is a (or the) major preoccupation of the game?
2. If the answer to (1) is yes, is it also possible to have RPGing in which meeting challenges is a (or the) major preoccupation of the game, but skill does not loom especially large?
3. If the answer to (2) is yes, is it also possible to have RPGing in which outcomes in confronting challenges turns more on what the players do in the moment of play than on prior input from players or decision-making by the GM?
Prior input from player might be the build of the character - so that when challenges are confronted, this is a (perhaps the) significant determinant of how things turn out. My impression is that at least some 5e D&D players in this way. (And not because of any particular skill in PC building, but because of what the participants take to be the connection between choice of class and archetype and the process of action resolution. The notion of "spotlight" I think would be closely relatd to this.)What are some examples of - "prior input from players" and "decision-making by the GM"?
Some of Classic Traveller play is also like this - and there is very little skill involved in Classic Traveller PC building! For certain sorts of situations (maybe they're not really challenges, but I'll set that to one side - I'm thinking of routine encounters with officials, of routine operation of a starship, and of buying and selling trade goods) it is the skill that is brought to the situation rather than a decision made in the moment of play that determines how things turn out.
Examples of GM decision-making might be deciding what happens next without regard to what the players do in the moment of play. Many TSR and WotC modules advocate this sort of approach.