OKRs just means you write down measurable goals in a place where people can see them. The word is popular since it is obviously a good thing to do, it is something everyone should do. In school your OKRs are your classes etc, having such short term measurable goals is really good for personal productivity and alignment.
So OKRs are like unit tests, you can do them badly but it is a thing you almost always want when you do software development, unit tests aren't just a "buzzword", and neither are OKRs.
The alternative to OKR is that your manager writes down your OKRs in a hidden place where you can't see them, the only thing that changes is that now you are less informed. Ignorance is bliss, but reality will smash you anyway.
Personally I thought it was good that I could see what goals my manager had, what goals his manager had, what goals that managers manager had etc. I don't see why people are so angry at that level of transparency.