Really fun video. Getting a consistent group together is probably the hardest part of running a game. If you can enjoy a game with even as few as one or two players, that can work well.
I use a few tricks to keep groups going:
Have six full-time players.
Have two "on call" players – these are players who are interested but might not be able to commit regularly and are willing to jump in when a spot is open.
Run with as few as four. This means it takes five people cancelling before you can't run a game.
Run at a consistent time each week.
Run shorter games – I go for 3 hours.
That's helped me keep multiple groups going for ten years with one group consistent for about 20 years.
My solution is to run with as few as 2+me (the DM), and use a play structure that doesn't require the same players to be present at every session. We always end rhe session in a safe location (town, safehouse, etc). If someone can't make it, they're just in suspended animation along with their gear and hirelings/retainers until they're back.
Just not sweating the fact that it's a game has gotten me a very consistent game every two weeks like clockwork.
You don't even need to have someone else running their character. Just say that the character is busy/drunk/sick whatever match their role-play. Or simply have an agreement with the PC that despite being unrealistic for the sake of the game, nobody will wonder why a character can be absent in the middle of space or a dungeon without any justification.
I understand that in game with a big focus on party balance/tactic it may-be different but this kind of the game is the exception not hte norm