Hear hear.
I love itch as a platform, I really, really do. But with the lack of filtering/sorting options (I'm aware that it's being worked on, but I think it should have been done a long time ago), the barebones app client, the game library and collections' lack of features, it's all really unfriendly.
On top of that, you can only view your purchases on the website, not games specifically, so you would have to sift through each one in order to find a game instead of a game asset or tool. So I'd have to use the app, which like the website, is stuck in a listed order instead of a grid, which is just plain inconvenient.
A personal gripe as well is the inability to claim games that are free, like you can on other platforms. I have a lot of games in my collection that will likely stay in a collection instead of my library until I get space to install them. It's just a preference thing though, I don't expect anyone else to share it.
I don't want to stop using itch, but as we speak I am putting every single one of my games in my library into collections based on their genre because 1) there is no genre/tag filter, and 2) you can't add multiple games in a collection at a time. It's just really exhausting right now.