The only reason people are still upgrading REMs is because they promised to improve them. Yes there are people who are always going to be motivated to keep playing, but that doesn't mean things haven't slowed down. I'm sure you know as well as any guy selling marrows that for those 2 weeks or whatever after Delve where everyone was going apeshit the sales slowed down quite a bit. It's recovering but we're still in that phase where a huge amount of people are unmotivated because they have no idea if working on something right now is even worth it.
1. Work on a delve weapon and they rebuff REM to be better -> waste of time
2. Work on REM for a waste of time now, rebuffed REM still don't match up -> waste of time
I rarely ever agree with pchan but I do agree that the expansion has been kinda lukewarm.