I haven't even bought a 5G phone yet. My carrier keeps threatening to cut 4G coverage in various areas, and has already axed 3G entirely, rendering large swathes of otherwise perfectly functional devices useless. So far my 4G Moto Z still works. For now.
At this point my conspiracy opinion that the constant "generation" changes are mostly to just force people to buy/lease new phones and devices. Even pokey old 4G has always been more than fast enough for all of my mobile internet activities. Hell, even 3G was.
I have no less than four otherwise flawlessly functional phones in a desk drawer that just won't work with my cell carrier because they've either turned off 3G or discontinued the specific 4G bands those devices need.