I can trust your intention without trusting your skills - if, in order to have fun with the game, I need to first make sure the dm is good at running the game, a set of skills not measurable by knowledge of rules, systems, or other provided knowlege, then any time I join a game it's a gamble as to whether the game will be fun. Because maybe you're not good, and my evening will be crap. Unless you know of a reliable method for judging the skills of a dm that's noticeably easier than playing with them?But this seems to emphasize the fact that trust between players is a key element to an ttrpg unlike video and board games with more defined rules. Not only because of dm discretion as the referee and final arbiter of the rules, but also because of ‘problem players’ of various kinds. I think without that trust and level of communication rpgs are not worth playing. Story games do a good job of providing advice for both gms and players for how to approach the social situation of playing an rpg.
Also, if I don't play with unskilled dms, how will they get skilled? (Answer: systems to guide them, but you seem to be arguing against using systems to guide the game, so what else is there beside 'fail a lot and drive away players'?)