As a curious example of structure and guidance to help players not have to ‘do [GM tasks] cold’ as @yoshi mentioned, I’d love to recommend Ironsworn as a cooperative (GM-unecessary) game that is very accessible for people familiar with more traditional GM-led model games. I’d call its mechanics more GM-unecessary or GM-optional than any other term, since you can have a GM, but you don’t need one, and neither do players explicitly need to take on many deconstructed GM duties. They can play through a satisfying story while feeling like ‘just a player.’ I’m not fully sure how, but it works.
Players all have a pretty traditional PC/protagonist, with stats, goals, etc. The game’s systems—especially the moves and oracles—provide nearly all the direction and authority that a GM typically provides, so players don’t tend to feel like they must invent on the spot, or take up GM authority in any particular way. It handles typical GM tasks subtly in a way that feels like there’s almost always a next step to move forward, either mechanically or narratively, depending on how inventive players are feeling.
For instance, if anyone doesn’t know what to say or what happens next, we can disclaim decision-making and either use the Ask the Oracle move, trigger another move that seems appropriate and seek inspiration from its outcomes, or just cut to the next moment we can think of that could serve as a milestone toward one of the many goals mechanically in play.
Likewise with scene framing or world-building or opposition, the game is intended to guide you to introduce these things organically based on either move results, or if you have questions—like “Is anyone here?” or “How dangerous is that thing?” or “What do they want from me?”—ask the oracle with a die roll. A series of yes/no, either/or, or even keyword oracle rolls can produce surprisingly apt and gratifying directions no individual person would have driven the details, which, wth the help of human minds always seeking patterns, eventually makes the story feel like it really has a weight and will of its own. It’s pretty wierd.
Granted, many players have trouble conceiving of the mind-shift necessary to play it entirely solo, though I would argue that is usually because they undervalue the importance of firmly and clearly committing to declared truths or ‘on-screen’ actions (vs potential/hypothetical action options), since play gets awkward if a solo player leaves too much ‘in their head’ and thus tries drawing story out of a growing heap of noncommital, nebulous, Schroedinger’s Cat non-details. That’s an issue for solo only though, because as soon as you’re collaborating with someone else, you have to talk and declare things out in the open, as it were, and commit.
That said, I’ve seen far fewer players, even from traditional backgrounds, have issues with the core cooperative play that doesn’t need a GM, but also doesn’t really require anybody to take most of the main GM duties. I think there is a lot to glean from Ironsworn’s setup in terms of GMless/GMful theorycrafting. It somehow works to create coherent stories while letting players feel like they’re ‘just’ players. I wish I could analyze to the heart of how it achieves this, but I have yet to put my finger on it.
For the record, I have no affiliation with the game or its designer. I just like it. 
