iPhone Battery Replacement

I'm either too lazy or too cheap to follow Apple's never ending phone upgrades. Until a month ago, I was still using my old iPhone SE with a bad battery. That got replaced by my sister's old iPhone 6S with a bad battery. My mom is still using her iPhone 6S+ she got at the same time as my SE, and my dad was using an old 5S until my sister gave him another iPhone 6S with a bad battery. Oh, I forgot to mention that my mom's 6S+ also has a bad battery. This is why I hate Apple. I have a Samsung S5 and it's easy to change the battery. I understand that they have to waterproof the phone now but at least make it easier to service and replace the battery. Also, 4 out of 4 phones need a new battery after a few years? This smells planned rather than coincidence. This is coming from someone that has owned an Apple II+, Mac, Mac IIse, Macbook Air (battery replaced), multiple iPads, and whatever else Apple makes. Love their products; hate their battery policy.

Anyway, I purchased a 2500 mAh battery for the 6S and my dad is replacing it now. He successfully changed out the battery in his 6S and my mom's 6S+ so I'm letting him do it. I did replace the battery for a 3GS a long time ago, and more recently in my Macbook Air, but my close-up eyesight is not as good anymore.