I grew up playing with K'nex a whole lot. K'nex's functionality completely relied on the sturdy yet flexible plastic. Everything snapped together and K'nex worked because they snapped together hard.
Now as an adult in her thirties I'm getting into Gundam and especially gunpla. Gunpla have way way more engineering problems to contend with than even a large complex K'nex set. That being said plastic is really all over the place in quality. Gunpla require multiple kinds of plastic, some extremely rigid, some meant to bend and deform to fit. But it feels like they haven't figured out exactly what plastic to use for each situation.
That being said newer kits, witch from mercury does this, have done away with a soft plastic that gunpla fans have disliked for years. And the witch from mercury kit I put together, Beguir-Beu, felt a lot sturdier than my Iron blooded orphan mechs.
There's always going to be some kind of back and forth with bandai between costs and desire to release quality kits. But I hope I don't have to worry forever about my metal wives having hip problems.