This has been the case for me with the Dock for twenty-plus years. You can't kill the Dock. You can hide it. You can set the delay until it appears. But you cannot kill it, it just respawns.

And it's such a terrible waste of memory/screen space/an edge of the display.

And of course I said yes, and Apple said no, to Launchpad, an actually useful tool ¯\_(ツ)_/¯