The Tueller principle states that they can get you within 21ft...if you don't move. It is taught to military and police officers not to say "so you may as well not even have these guns we're giving you," rather to say "move laterally as you draw if possible." Often accompanied by phrases like "move off 'the X'" ("the X" referring to the spot you're standing while the encounter/your draw starts.)

Furthermore even then I'd rather be able to shoot from a thumb pectoral index and use my left as a leveraging arm if need be than be in an entangled fight over whatever contact weapon he brought, and that's assuming I'm lucky enough that the violent intruder doesn't have a gun of his own, which is frankly a bold assumption. Also assumes he's alone and didn't bring the typical 2-4 friends.

Feel free to make your own choices regarding self defense, by all means, but you fundamentally misunderstand the Tueller principle.