Working with Jenkins CasC, JobDSL and declarative pipelines, I'm not sure where the million times comes from. Sure, there are some annoying parts, and GHA has the social network for reusable actions, but apart from that it's not that different.
Oldschool maven type jobs where you type shell script into a `<textarea>`? Yeah, let's not talk about those, but we don't have a single one left anymore.
Jenkins Groovy is awful and full of footguns. Have you ever run into a serialization exception?
It's too powerful and there are too many of its implementation details exposed to the user.