The reason Jio paid costly for minimum (except J&K) 10MHz Band5 Pan India is these small phones...
I have tried them once (yaer and a half ago). The xp was not that good to give it to my old staffs in office. Button press response, contacts response was not great (at that time) and those are the bare minimum. Whatsapp, fb, yt, browsing on button phone is more like a gimmick, imho. Once they get them right, we can say good bye to 2G and feature phones. But that day is NOT today or this year, afaik.