I'd love a return to the old snap-fit plastic cases. Besides the ease of battery replacement, those phones seemed much more durable. Maybe because there was something that gave way on impact? I remember watching in horror as the plastic cover of an old LG shot under the display shelving at Home Depot at approximately the same speed the phone hit the concrete floor. I never used a case with one of those phones, nor did I ever crack a screen. It was tricky digging that cover out from under the shelving, however.
Phones currently can be dropped in the toilet with zero damage. It is a real benefit to have waterproofing. I would prefer waterproofing over easily replacing battery that happens rarely.
Unless I forgot one, I think I'm on my 10th mobile phone in total since the late 1990s, so averaging just under 3 years per phone. And I think the interval was shorter in the feature phone days and longer in the last 12 years or so where I'm now on my 4th smartphone.
Maybe it's because I learned to be careful with my phones before smartphones existed, back when dropping it might mean the back cover, battery, and main body flying in different directions. As a result, I'm also the kind of person who might drop his phone/wallet/passport into ziplock bags if I was heading outside with a chance of significant rain...