I personally think that a battery is removable enough as long as it can be replaced with screwdrivers (maybe a hot air gun) and no additional parts need to be replaced as well.

My phone can be opened from the back with screws, no glued glass that needs to be replaced. The battery is probably glued to the metal frame, but that is OK because only the battery that gets replaced is going to be damaged. Some batteries even have a pull tab that pulls the adhesive out from under the battery.

I can understand why batteries are glued, because screwing them isnt really possible and its better if the battery doesnt flop around inside. I can also understand why they moved away from completely user removable batteries because those really take up quite a lot of space.

But it should be possible for reasonably tech savy people to change a battery in 15min. It shouldnt be that you need hotplates and have to destroy multiple phones before you have enough experience to open them without damage.