1xx is the response code you try to ignore because it's really annoying to deal with properly (like when you receive a 100 response to a file upload, or even worse, a 101 with a protocol that isn't exactly what you expected, or a 103 which means more content comes later).
1xx response codes are crucial for things like WebSockets and HTTP/3 but they make the HTTP state machine more complex and many people writing manual HTTP requests are ill-prepared to deal with them.
3xx - Somethings could be better
4xx - You did something wrong
5xx - Server did something wrong
Judging by this quick cheat-sheet I just created, this was not your fault :)