That also is/was awful. But it's just another platform like GHA, and the solution to this kind of thing is always the same, should not be surprising, and is boring in the good way. Write automation so that it's not tightly coupled to the platform on the backend. If you can't migrate between platforms then you're eventually going to be unhappy.
If someone is forcing you towards high stakes tight-coupling with no thought whatsoever towards the lock-in, you should get it in writing that "we at ${org} are fully committed to ${vendor} with ${platform}, on ${cloud} using ${tech} come what may, now and forever" and lots of sign off so that everyone knows who to blame when this is inevitably wrong.
YAML is just a data format. Make your own "thing" that takes input in any format you desire, then dump it to YAML. (also, YAML is dynamically typed, and supports explicit typing, but the parser can choose to ignore it)
I grant you pipelines are the best bit about ado, but the fact that you can’t test them is a pain.
And the webhooks and templating are pretty messy and unpleasant quickly.
We’re changing from ADO to GitHub (had to be an MS product for corporate) and the infra people are looking forward to GHA as they prefer their maintenance to ADO pipelines.