The easiness of replacing the battery has gone up with iPhone 7/8/X compared to iPhone 6. You can verify this on iFixit guides. The iPhone 6 is _relatively_ easy to replace because you don't need say a heatgun. You do need some special screwdrivers which you gotta buy. You can, on iFixit. I just bought a whole kit (on sale during Black Friday).
> I've bought dozens of Android replacement batteries and the only batteries worth the cost of shipping were actual real OEM ones. And those always cost >$60.
20 EUR for mine: https://shop.fairphone.com/en/spare-parts/fairphone-2-batter...
Replacing any parts on my phone is very easy. Only thing is that the main module with CPU board etc is ~300 EUR.
It really is DIY. There are thousands of guide that can be followed successfully.
Now, I completely agree with the design decisions of the iPhone. The completely sealed body is great for water resistance and having the battery replaced is still pretty cheap, especially if you use (I usually just let someone replace with a 3rd party battery for cheap, as this usually takes place after warranty expired).
The battery needs to have extra space (or bad things will happen) so it effectively has to be fixed on one side inside the body. Gluing it is a pretty cheap solution to that problem.
I've bought dozens of Android replacement batteries and the only batteries worth the cost of shipping were actual real OEM ones. And those always cost >$60. Knockoffs would start out decent and then die within a few weeks to months.
Apple's approach gets my vote. You get the upside of built-in battery and the peace of mind when you do need a replacement.
[Just to balance that, let me be clear that Apple's choice with regard to crippling my phone pisses me off. I just replaced an iPhone 6 that felt painfully slow and now I know why (I had tested the battery and it was at 75% -- I didn't realize replacing it would speed up the phone).]