No. I have not seen a system, that does not boils down to "DM decides".
Maybe if you use 4e, you could always use "level appropriate DCs" and still, the DM decides if it is easy, medium or difficult, how many rolls are necessary and so on.
If you have an adversary DM, there is nothing a player can do to "win". Some games make it more obvious that DM and Players are in an arms race, some not. Is it fun? No. But no system can save this group.
Okay, you haven't seen one. They do exist. Your experience seems to be with systems where the GM is the assigned arbitrator of when rules even apply, and when they do, they get free access to the bits and bobs of that machinery to tinker it to however they, the GM, thinks it should be. And, yes, in this case, if you have an unfair GM, they can apply this authority unfairly. (I switched from "adversarial" to "unfair" because the GM darn-better be adversarial! It's their job! They bring the adverse stuff for the PCs to overcome! What they should also be is fair and honest in bringing that adversity. It's not being adversarial that's the issue here, it's being unfair.)
Other systems take things like DC out of the GM's hands. Take PbtA, for instance. Here, every roll is 2d6+modifier and the outcomes are always 6- failure, 7-9 success with cost/complication, 10+ success. Individual moves may outline what success/failure/consequence is specifically, but the rolls are all the same. The GM cannot add or subtract modifiers from rolls -- any subtractions will be from previous failed rolls telling you this occurs, and additions are Stats or outcomes from previous rolls that say to add one. The GM can't monkey with this. Further, the GM cannot say "no" to a player move, and they are required to invoke the mechanics when they apply. So long as players are within the fiction and genre, the GM can't block actions. This system is not "GM Says" at all. Everything is in the open, there are no secret notes, you play, see what happens, and then go from there.
Do you have to like this system? Nope. Not saying it's even better or worse. It exists, and works, and isn't GM Says. Other games do the same thing in other ways. These games tend to radically differ from D&D in that the GM can't really prep play -- how can you when the next action might seriously alter play trajectory? They offer clear tools to assist the GM in continuing to provide situation for the players, to push that honest adversity, and even tell the GM to not play nice -- pour it on. Not playing nice isn't not playing fair, though.
Let me provide an example for my Thursday game where we're playing The Between, a PbtA/Candlewood Bay game. In this, my PC was confronted with a young man wrestling with an older for a gun, while claiming to have been kidnapped along with his sister. My PC is a noted gunfighter, so when I declared I drew and shot the older gentleman, this triggered the need to resolve the action (this is demanded by the system in this case). In this game, this triggers the Day move, or a move that you make when doing something risky or dangerous during the Day phase (where stakes aren't as high as the Night phase). This requires the GM to ask the player what they fear will happen -- what bad thing will occur if this move fails. Since this is a conversation, the GM suggested that I might be afraid I'd hit the boy. I said no, absolutely not, me shooting the boy is off the table because my character, as a renowned gunfighter, wouldn't do that. The GM said okay, what then. I said that I couldn't line up a clean shot before the older man gained control over the gun and shot someone. The GM obliged, I rolled 2d6 +Vitality (which was 1), with advantage due to a playbook move, and scored a 13. This is 10+, so the older man was felled with a round right between the eyes. None of this relied on GM Says to resolve. Further, since this game has a result for the Day move for 12+, the GM was required to provide some extra benefit or advantage. Here the
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