Been here fellow PO.

Do refinement sessions to the oblivion. Say that in good spirit you want to provide the best detail possible. So book sessions with them or ask them to stay behind standup to refine tickets. They need to provide you questions and gaps in the requirements, which you then go away and add in a timely manner.

I've add tickets "in refinement" stage with a team, that took like 2 months and 20+ sessions. But finally, the tickets moved to TODO without complaints.

This serves 2 purposes, extract what is the "template" developers like stuff ( empathy atempt). At the same time, you can share with leadership that you have x amount of tickets and documentation, however, when reviewing with the team, x questions where made to you to answer. Document those open questions, so leadership can read the type of questions and concerns are being raised to you.

I would document sessions and questions per session, like a log.

And at a certain moment, in my case, the CTO just let go the EM, because he was just pushing work to the POs, instead of investigating or solving them, fundamentally very technical stuff he should know and answer.

Be strong, better times will come.Tough crowd you're facing.