Each "flaw" that most people complain about has its reason.
The legs don't move!
This was done for stability. If the legs did have a swivel or something, the whole thing would wobble and/or compress the set down from activating the function.
Using CCBS legs would've fixed it!
The set itself already has seven CCBS joints. Adding any more would increase its weight and extend the price per parts count. Besides, the leg pieces that were used look fantastic to me. Very creepy, skeletal, and bug-like; something CCBS wouldn't be able to pull off.
Scorpio would've been better off as a titan set then!
I don't work for Lego, but i'm pretty sure that it was their fixed plan to have 4 regular sized sets and one large titan set. I don't think that the designers would've wanted to reformulate that plan completely just to fill out Scorpio just a bit more.
The function looks ugly!
I agree to an extent, but it's not as ugly as it could've been. They made it so that it would be easier for kids to grip, having an extended trigger, and the function works phenomenally; good for play. If you look at other Technic functions, in other Technic sets, those are way gappier. Besides, it fits the skeletal look just fine IMO, and it's unique.
it would've been better off without that stupid function!
It can't have a gearbox. A crawling mechanism would've too parts consuming. A tail function had to be implemented. Every set has to have a function.
The colours clash!
The colours are well dispersed IMO. Two (or four closely together) trans orange pieces on the claws, and two trans orange pieces on the tail; both the same width apart.
The neon green bits are packed closely together in the body, barely interacting with the red bits. Even so, the contrast looks nice. Imagine if it was completely neon green. it would look bland compared to the rest of the Skull villains
It's those claws that really break it for me. I'm sure they wanted it to look alien-like, but they just look straight-up ugly and deformed. Even the animators thought they looked ugly and gave him new claws!