Well old tank is old tank unfortunately. If those destined for Russian army frontlines. They might not be very suitable. But if they're destined for LPR/DPR unit or "new" territorial defense unit in occupied territory in rear line, they would be suitable.
It actually depends on what are the threats facing Russian tanks.
T-72/T-90 were designed to be much more survivable than the T-62 against threats were materializing in the early 1970s to late 1990s, and what future threats were expected to materialize over the next 10 years or so from the vantage point of those dates.
that does not automatically mean they remain substantially more survival than the T-62 against threats that have materialized that were not anticipated at the time of their specifications. For example, Against top attack by weapons designed to defeat ERA I suspect the T-62 would not fare significantly worse than most T-72/T-90. For that matter I suspect a Sherman wouldn’t fare much worse either.
it could well be that the russians did an analysis of their tank losses and concluded major portions of existing T-72/T-90 inventory were in fact not substantially more survivable than the T-62 against major portions of the threat. If that were the case, then it makes perfect sense for them to pull available T-72/T-90 out of the line for refit and modernization, because their modernization value and potential no doubt remain much greater, and make up the temporary front line shortage that causes with T-62, which for the moment would perform almost as well.