Orks are brutal if unsophisticated warriors, yes, but if you take out their humor that's ALL they are. No complexity possible, no interesting nooks, like stereotypical Khorne Berserkers. And humor doesn't help much either. It's just... they're not even alien. Merely boring. Tyranids at least have a neat aesthetic, but that's it, again zero depth beyond 'om nom nom'. Villains having some sort of motivation or complexity isn't a bad thing, people. Look at Chaos Marines, or even Daemons. Mind you, taking out Orks massively changes 40K. I'd prefer to have them 'fixed' like the Necrons were.
The Beast arises series proves you wrong in all those aspects. It's not just Orks physical size and combat prowess that grows with their evolution, but their society and culture as well, to the point they're capable of fielding diplomats.