It's an old Beast Wars joke.
I know. But it gets tossed around with the implication that it's inherently better than not having diecast and/or the complaint that it doesn't show up in modern products. Which it does. Not mainline, no, but it's still very much used in modern Transformers today.
Just that expecting a toy in a retail line to have to it is a bit ridiculous. G1 Prime is supposed to mimic the original figure, but add joints ala Missing Link, but has to do it at a modern retail line budget. So that means both a hollow chest/truck cab and plastic construction.
So ofc it's gonna feel light. I don't think that's a mark against the toy. Just a reality of concept and budgets coming together. If you want an articulated figure based on G1 Prime and don't want to or can't spring for the ML release then this is the option. And I don't think it appears "too cheap" given both the reality of budgets and the idea the designers were going for.