I'd like for the titlebar's buttons to be clickable on crashed apps. Currently you need to use the panel, or the System Monitor.
They are for apps that draw a titlebar. For apps that don't, it's impossible, and it's the app's problem for not drawing a real titlebar. Which apps are you seeing this with?
Telegram flatpak
Which uses CSD by default, meaning it's the app's problem. If you want this to work properly, enable the system titlebar in the app's settings.