Found this video really interesting as I have a relatively large backlog myself. Fortunately not nearly as large as this one.
Personally, I’ve only ever considered games I own to be part of my backlog, which makes my list much more manageable. That said, I have a large number of unplayed games on both Steam and GoG. So to start I’ve decided to play all my GoG games first (as that is still within reach). I’ve promised myself not to buy any more games untill all my GoG games are either completed or marked “did not finish” due to it not being my thing.
Some people just do it this way. This doesn‘t mean they don‘t have fun. I noticed this happens with books too; people buy books and then track how many they‘ve read, set goals etc. Some people think it‘s stupid, but for some it‘s fun.