What happened to iTunes File Sharing in macOS Catalina?
It’s in Files as of today. Just tested exporting a zip file from lumafusion for iTunes file sharing and when I go to Finder on my Mac, click on iPad, then files option, then lumafusion app...I can see the zip file. But I was only able to delete it. I could not copy it to my machine, might be a bug in the current beta. I have iPadOS and Mac OS Catalina most up to date public betas on these devices as of today.

EDIT: If you want to copy files from your iPhone to your mac, simply drag the files to a folder in your mac.

Photo below of this process on my Mac: