Very very difficult to make. Until now the penguin game ist the click game coming closest to a professional rts like starcraft or command and conquer. As far as i know.
And also this is quite buggy and feels different in gameplay compared to "real" games.
One of the hardest things to code will be the enemy ai. You have to make it think like a human when building a base, making him recognize the terrain an resources aroung him and at last finding a strategy to kill you.
I dont know your skills with click products, but if you are quite noobish, you should start with something else. Making a really good enemy ai in a simple shooter is difficult enough and something you dont see very often. I would look forward to a starcraft shooter btw
A game on the scale of starcraft can be made just as easily in Klik as in C++ or any other language, the networking features aside. The issue is that an RTS on a large scale is going to require a LOT of looping, something MMF2 just can't handle. Thus if you want a good RTS engine in MMF, it needs to be small scale. Simply checking what units are in range of each other every frame for attack collisions is probably enough to slow down an MMF program with the amount of units starcraft would have in it.
You can make a RTS in TGF too but you will still need to be a real pro of clickteam products. So if you're relatively new, it doesn't matter what clickteam product you have, it will be "extremely" hard to make a RTS as your first click game, I'm not saying impossible but "extremely" hard
StarCraft is a very complex game. In order to make a clone, you have to know how it works from the ground up. I'd really advise against aiming for something on level with StarCraft, but instead make something much simpler.
Typically, RTS games use a 32x32 grid that everything can snap nicely into; StarCraft, if it even uses one, has a very small movement grid of 4x4, while placing buildings goes onto 24x32 grid. The end result is a very rigid base building system, and a rather precise unit movement system. The problem with making a StarCraft is that there is a lot going on, without any user (or CPU) input. Every unit has to be able to find the fastest way from point A to point B; They have to dynamically know where they can and can't go. Most collision detection in SC isn't based on a grid, but rather a collision mask. If you watch any professional SC gameplay, you'll also see that a lot of the maps are designed specifically to utilize these collision masks; They're most often used to create unit specific pathing, where a small unit like a Zealot or Hydralisk can get through, but not a Dragoon or Siege Tank.
On top of unit movement, units also have to instantly respond to commands. Again, with pro SC gameplay, you'll often see units always moving in battle. A protoss shuttle may drop a reaver just long enough for it to launch a scarab at a tank in siege mode before picking it back up before the tank can fire back.
There is so much working in the background that I could probably write a paper just about how StarCraft works, without getting into any of the unit balance or stratagem.