why won't some of my software will no longer work with Catalina OS?

See the following from https://support.brother.com/g/s/id/os/macintosh.html

The Brother ControlCenter2 is not supported by macOS v10.15.

Use the Brother iPrint&Scan or Image Capture as an alternative function.

At a guess... because that software needs to be updated to a current version. Check the vendor's website.