Yeah, I know that it says " Due to technical reasons the following plug-ins and technologies have been removed from the product scope", so I guess I’m looking for a deeper answer 
What does that mean for projects from before v11 that used those plugins?
That you must put the dongle on a shrine and pray it doesn’t break.
I use Prologue and Mystic often, Spector not so much. It seems that 11 and 12 will live side by side on my PC for quite a while!
I won’t miss the synths that much (never used them outside of checking them out), but Loopmash is quite unique.
Perhaps they’re gonna replace it with a new audio FX, taking inspiration from StutterEdit, Effectrix, Turnado, Infiltrator, etc. It seems the new crop of Cubase devices (Imager, Squasher, Raiser, FX Modulator, even Frequency2) are aimed at replacing popular VST plugins with native solutions, so there’s hope
I’ve used Prologue once in a while, but I have to admit, it wasn’t so particularly sophisticated that the parts could not be replicated in any number of synths. Nevertheless, I’ll keep my Cubase 10 on my machine for a long time once I upgrade!
Highly disappointed LoopMash is not in C12. It is a fantastic plugin. I paid money for an upgrade to C12 and lost one of its best features–including mystic and prologue. WTAF steinberg??