If you look at the PMBOK (Project Management Book Of Knowledge) it is really a comprehensive list of all the things you might have to think about while running a project. All of them are relevant to every project (e.g. hiring, communicating with the public) but some need a lot of attention for some projects and others don't.
I've worked on "A.I." projects where the sprint involves running a batch job that might take two days if it all works right. If it doesn't work right you might have to retry a few times.
When I was in charge of that batch job I would start it as soon as possible, sometimes with a week and a half to spare. Whenever somebody else was in charge of it they would start it with half a day or a day to run and we would blow the end of the sprint.
I blame the continuous stream of "urgent but not important" communicates generated by agile for that.
The timeboxing of planning is also a very bad idea. I worked at a place where we had a timebox of 2 hours for planning but really after that we were nowhere near a realistic plan for the sprint and it would take another 2 or 3 days of knock-down, drag-out meetings that would leave us all exhausted to understand what we had to do. After that the work was mostly downhill, at least the way I saw it, but one of the other team members would consistently burn the midnight oil at the end.
Often agile "teams" have a "normalization of deviance" situation where they have to do one thing (or say they are doing one thing) so they can say they are sticking to the process, but actually do something entirely different to get the job done.
That's sad.