No, it’s not about power. You did no research and went blind ahead with BGE probably because it was the only software you could use. Then after you learn you got way in over your head with iOS and Google Market talk you blame it on BGE not being powerful. People make beautiful games on it, it’s a matter of who’s in charge.
Besides Rockstar has already raided both the iTunes AND Google Play with their selection of genuine quality GTA games for a very lucrative prices and there’s zero room for competition. If you attempt to use GTA-specific stuff in your game you will be sued.
And I might add running a 3D sandbox game on mobile device is a serious challenge to any engine including the very best ones and you’d have to be a wizard coder to make it work.
When you know so little about the industry and business it doesn’t matter what you use, you aren’t going finish this kind of project. Start smaller.