Yeah, I recognise that disc-based systems are inherently less durable than cartridge ones, but there are still ways to make them more durable to a point. The closeness of the components in the Wii is one example, which is what can cause the GPU melting especially if Standby mode is/was used. There are other things too, like how a flip-top drive is more durable than a slot-loading drive, and Wii's ability to accept the smaller GameCube discs made it a bit weaker as well. I think Nintendo also used to use higher-quality materials than they do now.
The GameCube is a disc system and it's more durable than a Wii. The verdict is still out on Wii U, but the drive seems to be better constructed at least. I think it has more powerful cooling fans as well. I'm not going to be using Standby mode with it though, just in case.
I know they're not the only company doing these things either so I don't single out Nintendo. We live in an increasingly disposable world, everything's using cheap parts.