Yeah I watched the video, it's arguing against a problem that only exists with problem players.
I LIKE when players give me interesting backgrounds. I dont mind if its not lengthy, a paragraph or two is fine, but it is also 100% okay to give me 10 pages of a backstory if thats what they wanna do. As long as it is interesting!
Now, a good background isn't about length really but it is about information. It should tell me, the DM, what sort of character they want to roleplay and where there interests in my world lie. It should tell me how they are connected to the world. It should tell the player what their motivation is, it should inform them of WHY they are doing what they are doing. It should help provide consistency to their roleplay which, imho, makes for a better experience for everyone at the table.
I have had a players background be a problem exactly once in my decades of running games. We were playing 13th Age and he wanted his player to be the son of the Emperor. Okay, cool, I discussed it with him and told him the Emperor had a ton of sons so while I'd allow this, it generally wouldn't give him any material in game benefits at least not at the start.
The issue became that, in play, everything he did he would try to tie to his characters backstory...regardless of whether or not it fit. Regardless of whether or not we were in a session which had been exploring some OTHER player characters connection to the world. He would try to steal the scene, steal the plot, steal everything and I frankly would not let him. But it got to the point it was making other players upset and taking away from their experience so eventually because of this (and a couple other issues) I had to ask him to leave. TBH he might have quit in a huff, it was years ago. Either way, he was gone and the game improved.
Again though, that was not an issue with backgrounds or players having elaborate backgrounds. It was an issue with a player wanting to run the show to the detriment of the party and story.