If your PS5 storage space is filling up faster than you expected, you may want to double check that you aren't doubling up on backwards compatible games - especially if you tend to start installing games straight from your mobile app.
PS5 can play both its own games and PS4 backwards compatible games, which are treated as completely separate applications that each need their full respective room to install. As noted in a thread by the PS5 Reddit community, it's entirely possible that you'll have both versions of a game which is available on both PS4 and PS5 installed at once - as user DavidEgrrr reported, several games which he installed through the PlayStation app had both versions sitting in storage.
Unless you really want to go back and forth between the PS4 and PS5 versions to play spot the differences, you probably don't need both installed. Just head to your storage options and you should be able to see "PS5" or "PS4" next to each game you have installed, and you can start clearing the dupes out manually. This is especially significant for games like Crash Bandicoot 4: It's About Time, where the PS4 version requires just over 45 GB of space but the newly released PS5 version only needs 20 GB. The future is compressed.
Meanwhile, if accidentally downloading PS4 games is a problem you'd love to have because you still can't find a damn PS5, you aren't alone. According to the NPD Group, PS5 is the fastest-selling console in US history, and Sony is still struggling to keep up with demand.