Off the top of my head, the main advancement the T-62 had over the T-54/55 was the 115mm gun, even though it only appears to have a minor improvement in other fields. The T-55 saw a good number of upgrades and modernizations that kept it competitive with the T-62, even being introduced simultaneously. All of the effort put into the replacement seems like a waste with such little ammunition development that we saw for the D-10 gun, being a stark contrast to the life squeezed out of the L7/M68. As far as I know, Soviet designs like the ~1978 3BM25 round still possessed short penetrators whereas the M735 had a much longer (but weird shaped) one. I will admit I don't know much about APFSDS development, so there could be a legitimate reason to use short penetrators, as well as the fact I could be totally wrong about the 3BM25.
>TL;DR: Was the T-62 a waste when the USSR could've made better 100mm ammo?
Bonus question: Is this analogous to the M48 vs M60?