Agreed, I think they'll just never increase the free storage again. Eventually, people will get tired of quarterly inbox cleanups and just pay for the extra storage, which is a win-win for them and avoids a serious PR crisis.
If you are in the habit of exchanging a large amount of documents and pictures over email, a dedicated storage solution might be more appropriate.
Work-related communication, as in freelancing, might deserve a separate mailbox that is kept clean of unimportant things.
I could go on and on for what I'd consider a great cleanup experience. It's surprising to me that such a thing doesn't exist, nor is it the kind of thing that's built into Gmail itself. You'd figure they would be best to offer a simple cleanup experience that has sane defaults.