I am sorry to hear that you had a bad experience with Scrum. But I think that conclusion that you are making could not be further from the truth.

I will write post about it.

But TL;DR;

Yes, DS is a bit different from software engineering. And yes, estimates are difficult to make some times. But if you shift you focus from defined outcomes to artefacts of your work everything makes sense.

Also, PM is not all mighty member of a team. He/she is just another team member responsible for business priorities of the team.