"Updating Maven Project" blocks whole UI, not just updated project

I reopened a long time closed Maven Project.
Immediately a process "Updating Maven Project" started, visible in Progress view and on the lower right.

Waiting for that to finish I try to open a file from a completely separate and unrelated project.
A modal popup appears showing progress of several processes, UI behind it is grayed out and it is impossible to do anything.

- closing the popup does not help, the moment I do something, it's back
- cancelling the "Update Maven Project" process does not work. Red cancel button gets gray and that's it. Process continues, UI inaccessible
- restarting/shutting down Eclipse doesn't work either -- it still "Waiting for .... to finish"

I need to kill the Java process, but once I start Eclipse again, I am back at the same point.

a) why does a long running process block the whole UI at all?
b) why does a process (update, build, whatever) in one project lead to blocking everything in unrelated projects also?
c) why does a cancel does not actually cancel? Asking to cancel and waiting for it is one thing, but after a certain time w/o response, Eclipse should assume the process to be broken and kill it mercyless -- it should not wait indefinitely and even refus to shutdown
d) in this case it boiled down to fetch maven deps (jars) from a very slow repo -- such a bunch of http requests should really never block the UI, no matter what

A thread dump I took w/
`jstack `
[eclipse_updating_maven_deps.txt.zip](https://github.com/eclipse-jdt/eclipse.jdt.ui/files/10465406/eclipse_updating_maven_deps.txt.zip)