Sure, but unfortunately it’s not that easy at all.

You’ll often have to open the phone, which means you’ll have to remove the adhesive to remove the back or sometimes the front. With all the associated risks. Some stores that do this regularly have a procedure that doesn’t even bother them, where you get a new glass back, and it’s not worth the extra effort and expense of a new one to remove it neatly.

If you’re lucky, the battery can be removed, but with all those fast-charging devices, the contacts are tightly soldered. It is not a problem in itself, but it requires additional tools and skills.

Of course, it’s good that devices of more or less sizes are water and dust resistant, but installing a new battery is a big operation. Certainly not impossible, but not easy to do.

Now 4-5 years is still possible with one battery. But the charging port is also corroded, just like the control panel.
This can also be easily replaced if you are already inside. But phones with similar specs are often as cheap as a new battery + other replacement hardware + installation.
For example for Nokia 4 plus. Old Snapdragon 600 series inside, port and battery dead after 5 years of use. Of course, you can do something about it for €40 + €17 in hardware. But the Xiami Lite 5G clearance model only costs €55 more…is it a bit more premium in terms of hardware, lasts longer on battery, etc.