It was initially more union-esque to prevent being played off against each other and a dash of ideology. Then it became a cartel with the goal to to increase income / stabilize the market as well as a general international-economic-political forum because so much of their economies depend on oil.

Production limits were always a bit shady. Most meetings were just nations declaring what they'd (be able to) do and then a lot of talking to maybe see if things could be tweaked a bit and come up with a statement that made it look useful.

Their last 'success' was before Russia-Ukraine where they basically tried to suppress the price to make US shale too expensive and reduce its market share. Which happened. But again, debatable to what extend by OPEC's influence while they do write their own press release - with the explicit goal that the perception of power increases the price more.

Currently the entire region is going up in flames and allegiances are being stressed to breaking point.

The UAE leaving - as far as i can tell - is just a middle finger telling some of the club members its a farce and useless when it comes to its goals and (soft) powers, in the new reality of war & US export dominance. The middle finger being a political signal as everyone seems to be in disagreement on how best to handle the Israel-US-Iran war.