These days you can probably just replace "algorithm" with "audience". Make videos the audience wants to watch all the way through and the algorithm will love you. I'm 90% sure I've pinched this off mrbeast in an interview somewhere, he seems to know what he's doing.

E: Aye, this one. Timestamped but I'd recommend the entire video if you're interested in YT nerd stuff https://youtu.be/6pMhBaG81MI?t=472