People don't see the importance of optimising their code. It's easy to get things run smoothly on a PC, but every single % of CPU counts on Mobile. I was struggling with the same problem in my early stages of development, but as I learnt many tricks along the way my game now runs super smooth on mid range phones as well, even if my game is isometric multiplayer with Z ordering & collissions and tons of objecs on in the layout.
Many people just assume that if the game works on your desktop it will work on their phone, and are blaming the wrapper for bad performance. Usually it's bad code and lack of optimisation.
There are some tutorials and tips on the site on how to get your performance up, but i think the main issue is the lack of general knowledge on how the event system works that people just assume that it will work on phones as well.
I think we would see a lot of more good C2 made games with good performance on various app stores if people knew what they were doing, instead of blaming wrappers/C2 and ditching their projects.
Some more general "good practice" tutorials would be nice working with the event system, and understanding of how code actually works. It's easy to make things happen in C2, but it's hard to make them happen efficiently.