I think it is just hard to make an overall yellow-painted robot looks big, real, less-toyish.
Even when I search pics of those yellow construction vehicles online, without the background, they look like a toy.
Also I believe those super delicate metal scratches, stain of oil leaking, rusty areas and abrasive worn around mechanic joints are impossible to replicate by factory workers (unless it comes from a Three-A factory). But unfortunately those are the key elements for making this item looks realistic.
It looks great considering it's a mess-produced item as a statue collectible. But it indeed looks like a large-scale powerloder toy.