Yep, that's my feeling too. I don't know why more people aren't angry about these kinds of clauses?! It boils my piss, I've spent 15+ years developing skills, and I am still now allowed to own the fruits of my labour, produced on my own time and dime!
It's necessarily correct nor simple. I agree that the choice of words is too wide and companies don't make it easier to understand what is included and what's not, but as an employer I don't want my employees to compete with me while still being employed.