all my data practicaly are few big global tables of instances only
ya sure, globals everywhere.. why not?
Surely it's faster to hack together a small simple program like this... but do you really think companies investing millions should approach their software with the same careless attitude you show here?
Global state is a proven major source of bugs and general impossibility to maintain a software that grows beyond a certain size.. most modern language design is targeted towards eliminating global state and shared state. They DO require more thinking and pre-design of your code, but that's what might save the company from ending up with an unmanageable mess of spaghetti code.
I hope you understand that trying to propose a bunch of big global state in C-style as solution to any problem is going to get you out of any decent job interview in 30 seconds.