Linux has many and a set of low level responses to keybondings that must remain responsive that don't have a UI nor ability to kill individual applications.
To be fair in current systems Linux UIs normally remain responsive until memory exhaustion which is handled very badly. You will probably reboot before the oom killer assassinates the offender. The fix is a user space daemon like earlyoom which activates at a configurable level and targeting rather than absolute exhaustion when even killing the offender is challenging and usage has been hard for tens of minutes.
You or your environment can also set your UI process to a higher priority as far as processing and io.
If your UI doesn't remain responsive it's because your distro isn't using existing tools to achieve this.