SD card slot works fine in Android 5.x, a similar experience as in Android 2.3. One can install apps there, one can put private files there, it even support per app-storage there. Sure some old apps may not work with the newer Android 5 APIs, but there are usually alternatives. What do you miss, what do I miss?

And it's far cheaper to insert a 128GB SD card than buying a phone with such storage capacity upfront. Also changing a SD card or upgrading one is possible too.

Replaceable sim-cards/sd-cards/battery/etc are good for the consumer.