The VST plugin feature in RB/BIAB has a long history of either not being available (early 2000's) or not being able to sync (until recently).
If you're talking about RB tempo syncing with a plugin you're correct, that was just added recently but now it works so what's the problem? You're complaining because it took so long?
...it is still a long winded process to activate the plugins
In the plugin window you click "Select VST". This is long winded? Pretty simple to me.
RB has a high probability of crashing
If it crashes there's something not set up correctly. There have been some long and detailed threads where the user was willing to dig into everything step by step, he posted screenshots when asked and they all wind up the same place. He didn't check or activate something that should be checked.
automatic window sizing to match the plugin seems non-existent
The problem that lots of us have complained about for years is PG keeps that VST selection window open at the top which pushes the main plug window down. However you can hit the full screen thingy in the upper right and then scroll down to see your full plug in window. Clunky I know but it works.
I have just found that when using the latest S-Gear (Scuffham Amp Sim)the plugin screen blanks out if you change a preset??
Can't comment on this one.
If RB "dislikes" the plugin everything either freezes or crashes.
If you don't have it set up correctly then crashes can occur.
I cannot figure what I am doing wrong but the RB VST instrument feature for audio recording with input monitoring seems erratic and unstable?
I spent several sessions with my sister laying down vocals and the IM worked perfect. Same with me playing my keyboards. You need to use ASIO and have ASIO Always On and Input Monitoring checked in your Audio window.
RB certainly isn't perfect but the only real issue in your list is the screen blanking with your amp sim. I have no idea about that one.
If you think Reaper or Studio One has more and better features that's fair enough and I agree with you. All I'm commenting on is Real Band works fine as it is. Can it be improved oh yeah, absolutely and Pipeline and others have been pointing things out and important changes are coming like Rewire. Peter said around Christmas that this would be implemented early this year.
Bob