It's easier to pile on a lot of changes with AI assisted workflows. And reviewing all that is definitely a challenge just because of the volume of changes. I've actually stopped pretending I can review everything in detail because it makes me a bottleneck in the process. Anything that makes reviewing easier is welcome.

To me, stacked PRs seems overly complicated. It seems to boil down to propagating git rebases through stacks of interdependent branches.

I'm fine with that as long as I don't have to deal with people force pushing changes and routinely rewriting upstream history. It's something you probably should do in your own private fork of a repository that you aren't sharing with anyone. Or if you are, you need to communicate clearly. But if the goal is to produce a stack of PRs that in the end merge cleanly, stacked PRs might be a good thing.

As soon as you have multiple collaborators working on a feature branch force pushing can become a problem and you need to impose some rules. Because otherwise you might end up breaking people's local branches and create work for them. The core issue here is that in many teams, people don't actually fork the main repository and have push access to the main repository. Which emulates the central repository model that people were used to twenty years ago. Having push access is not normal in most OSS projects. I've actually gotten the request from some rookie developers that apparently don't get forking to "please give me access to your repository" on some of my OSS projects.

A proper pull request (whether stacked or not) to an OSS project needs to be clean. If you want to work on some feature for weeks you of course need mechanisms to stay on top of up stream changes. OSS maintainers will probably reject anything that looks overly messy to merge. That's their job.