Let me fix that for you:
I'm going to define an RTS for you: you build up X type of economy with Y system, you make buildings and tech, you build up an army THAT COMES OUT OF THE BUILDINGS and you kill the enemy. Any thing without such feature can't even be considered an RTS, just another crappy game that will be forgotten quickly(see DOW2).
When I found out about this in the Alpha it was a heart-breaking moment. Even more than the poor design(AKA I GET A PANTHER IN 5MIN NPNP) and the worst optimization possible.
EDIT: REALISM HERP DERP REALISM ERMAHGERD REALISM LELELELE WE DONT CARE ABOUT GAMEPLAY XDXDXD REALISM XDXDXD
There has never been a clear definition of RTS, aside from the fact that you control units from overhead in a real-time manner, and that you have to use some level of strategy to win.
Herzog Zwei was the first RTS, which wasn't really a base builder. Dune 2 was a base builder, and there were many others after that involved base building, but not always. I think back to games like the Sudden Strike series, Blitzkrieg, Men at War, Dawn of War 2, Homeworld, etc. These are all examples of RTS games without traditional base building. Even the recently gone beta / semi-released Airmech, a game greatly inspired by Herzog Zwei, is the same way.
Regarding the alpha, I have no idea what you're talking about. Performance was fantastic for me, and I never saw a 5 minute Panther. Buildings changing isn't a big deal at all in my opinion, if you read some of the coverage out there (i.e. PC Gamer) you'll learn that some maps have radio stations, where you can bring in units from other areas of the map. It'd be difficult to do that with traditional base buildings.