Gluing batteries solved the old issue where you would drop your phone and it would shut down.

It's not so much about them being glued in but that nowdays they seem to be glued behind display and al the rest of the phone while there is no access from the back.

How big an issue was that really? Pick it up and put it back together and it turns on again.

Adding a tiny strip of glue to the battery so it doesn't slosh around in the case is not a problem.

The problem is that you need heat to open up the device itself (all that is between the battery and the hot air gun is about 1mm of glass), followed by a bath in isopropanol and lots and lots of twaddling around with tweezers and spatulas to get the old glue residue removed from both the display and the case (risking damaging either in the process), followed by really annoying meticulous work to place a new glue sheet exactly onto the case (or display) to make sure it fits again. Oh and you always risk cracking the display while removing it.

That is a solved issue and has mainly to do with a badly designed connector and has been resolved since the late 2000s. Glued in batteries don't use any other connector than batteries that are glued in. And if your case isn't designed like shit a drop should not open it.

Try it with a modern Fairphone for example. I had one for years and not a single time the back lid fell off or the battery disconnected. I had a couple of batteries die in phones tho. General point: If you argue with people who have more experience on an issue than you, bring the receipts and red-team your own statement before you make it. Everything else doesn't really shine a good light on you.