You can absolutely learn to fly on a sim and solo a real trainer on your own successfully.... No question about it.
Possibly. Coming from someone who spent a tremendous amount of time on the sim prior to attempting to fly, I can testify to the value of a good sim (in my case, G3).
But there are a ton of essential things that my instructor taught me that I would not have learned on my own. Such as the proper and safe way to start the model, the boundaries of "the pattern", and the initial model checkout. Not only did he go through my model with a fine toothed comb for an hour, but he told me the "why's" of how things should be set up. Just the small tips he gave me during the buddy box sessions are worth gold to me now. (Like "Land the wheels, not the plane")
Plus, the smile on your face when you finally solo, and you turn to your instructor who has unknowingly walked back to the pits during your flight and starts applauding you on your first solo!