I agree with Nypyren's reply.
Also wanted to add that award winning games and studios are also using Unity for complete games.
Think Monument Valley and Hearthstone.
Time is a resource. The quicker you can prototype your game ideas, the more likely you are to spend the time to polish them.
C++ is great for truly learning how programming works at a deeper level, but you should decide what is more important - your programming ability or the product / game.