The T62 is actually really not as utterly horrible as it looks. They Re basically the same generation as the Leopard 1s.
The Ukrainians use them too. Both domestically upgraded ones and some modernized ones they got from the Czechs.
There's 5 things worth keeping in mind about the T62.
1. A shitty tank is better than no tank.
2. It's an extremely simple design, it's relatively easy to maintain and upgrade.
3. It has a 115mm smoothbore gun (the T55 has a rifled gun) that can fire APFSDS rounds, yes it's under gunned against a T72 and horribly undergunned against a Leopard or Abrams, the 115 is hella scary for infantry, MRAPS, Bradleys, Strykers, BMPs, M113s.
4. The ones the Russians are sending to Ukraine are the MV Obr 2022 variants. They basically have a new diesel engine, modern ERA and new sights with thermals.
5. About 22000 of these fucking things were built. Most of them are scrap metal or were exports, but the guestimates are that the Russians had about 2000 of them in deep storage. They pulled about an estimated 600 of them so far.
Would the Russians prefer to have T72s or 80s or something instead? Sure. But see point 1. It's still 600 to 2000 nasty metal boxes with a big ass gun on them that the Ukrainians have to kill.