Without a PM: I conducted customer interviews, wrote up product requirement docs (PRD), and iterated with design on the mocks. On top of that, I had to implement the whole feature (while tweaking things with a designer), and also juggling another track of technical work.
This would be fine if I was a founding engineer, but I'm not and wasn't being compensated enough for the extra workload. And sure, now with LLMs the coding portion would be smaller, but there would still a lot of context switching and one might not able to do technical deep dives into things with all the meetings. All those meetings.
So don't overlook your PM.