All my IMAP accounts filter to subfolders. I don't see IMAP vs POP as a consideration. What drives most POP users is the wish not to leave their correspondence on a remote server in the cloud. You can emulate the behaviour of POP in IMAP by setting up filters to move messages, on download, to folders under Local Folders. Gmail do seem to be discouraging the use of POP. They haven't offered their new OAuth2 with POP. They have introduced changes such that old accounts will still work, but new accounts need a new procedure. Have you gone to the gmail website to create an application specific password?