OP_RETURN and taproot annex both expand the data burden on future nodes so I'm not really sure what you're talking about. (A pruned node can't be used for an IBD.) 

Fake pubkey outputs are still pubkey length and therefore not any harder on validation than a normal transaction. They are also a pro rata donation to the rest of us because they will never be spent. Also you are not " driving those uses to fake pubkeys." I'm not driving the thieves to my neighbor's house by locking my own doors.

Steganography is not the issue here. If it looks like a normal transaction, the whys and wherefores are not up for debate.