Here's the thing about itemization in an ARPG, progression is mostly psychological.
At launch, getting all the items you wanted took some time, getting them rolled well took more time. You were probably well geared and pushing past the lazy crowd in 2 to 3 months.
Now you get you base gear in 2 hours and can smash the highest difficulty on day 1 of a season with no effort. Getting your items to be all ancients that are rolled well takes some time. You are probably well geared and pushing past the lazy crowd in 2 to 3 months.
The game now is like a mobile game. You have enough energy to make stupid fast advances in the beginning and then it levels off and there is very little distance separating the middle of the pack and the top end. The difference between launch and now is they hand you everything at a base level and then you ha e to work for it as opposed to working for it in the first place.
The RMAH didn't effect anything. The goal posts just moved. And guess what? My friends list has already started to Peter off this season, which I guess is longer then most seasons due to the two new sets. Removing the RMAH didn't really make people play longer. It just allowed them to go deeper easier.