I think there's two factors at work here.

When the movie toys came out, they were considerably more fiddly, and I think the plastic density was adjusted to be more malleable and fault tolerant. This was very evident to me when comparing Universe/Henkei toys to their Classics counterparts. The Classics were harder and firmer, albeit less fault tolerant.

And the second factor is the increased costs of production which has invariably resulted in a reduction of quality control.