I really don't understand the issue with this, at all. Plastic saves on costs, and is more durable than glass. I genuinely couldn't care less as long as the screen itself is glass (which the S5 screen was glass).

What's wrong with plastic other than marketing people telling you it isn't 'premium?' If you want to talk about shitty build quality, how about modern phones that are completely encased in fragile glass and must be kept in a case? I rocked my plastic/aluminum Note 4 for 5 years without a case. I still own it, in fact, 8 years later and it still works great because it's made out of durable materials just like the S5 that I owned before it was.