Mod Turns Dota 2 Into A Third-Person Shooter

That's why you don't like it. It gets really addictive when you learn the game and master a few heroes.

Thanks, fixed it :)

But why? There are mods for other Valve games too

That will come from the workshop, you won't get ban 'cause of it.

Absolutely not, Dota 2 has Workshop tools and you can load those mods ingame, you only play these mods with people also having it downloaded.
Valve restricts "addons" for Dota 2, so that only whitelisted ones aka new hero models, sound files...can be used that don't give you an advantage.