One of the reasons Rotom-A were considered the best spin blockers was not only their bulk, but the fact that they were immune to Spikes and Toxic Spikes. While this may not seem that important, in a stall vs stall match up, the player that lost their Rotom-A was usually put at a huge disadvantage.
None of the new ghosts have levitate and Gengar is far too frail to be blocking Rapid Spin. Burunkeru seems to be everyone's favorite new ghost but it hates Toxic Spikes. Nattorei may be outshining Forretress right now, but it's pretty ironic that Forretress with Toxic Spikes can ruin the Burunkeru/Nattorei combo on its own. In my opinion, the removal of Rotom-A's ghost typing was a step taken by Gamefreak to reduce the effectiveness of stall.