I use podman regularly, and despite it being a good drop-in replacement like 95% of the time, the 5% of the time where it isn't seamless are super painful. For example, skaffold (https://skaffold.dev/) pukes all over itself when you try to run podman as a drop in replacement. I'm sure there are plenty of other examples, but that one stops me from using podman at work in addition to in my personal projects.
I mean, really, if we keep in mind that formally these are 2 totally unrelated projects, it's hard to complain. Yes, it's almost seamless. But since when installing Podman everyone thinks roughly "I am installing a newer better Docker version", and we all already have a few dozens of custom Docker containers running, it's hard no to wish it was even more seamless and backwards-compatible. I remember the transition process wasn't nearly as smooth as I hoped, and every small glitch is kinda stressful, because you know that currently all of it "somehow works", and if something breaks you probably won't even notice right away.
Podman does not require systemd (thank God). I use a simple podman compose up/down in a user systemd file to automatically bring my containers up at boot, but other mechanisms are possible, like quadlets and init scripts.