IMO, unless the sinking of the vessel represents a total battlefield reversal and Russia has no more vessels of a similar nature to bring in, then I’d hardly call it a ‘strategic blow.’ More like a ‘tactical blow.’
Russia is very limited in the Black Sea and can’t bring anything in without a major confrontation with Turkey.
This ship was being used as an alternate method to deliver war supplies to Crimea as the land routes are increasingly under threat. So, while by no means a “decisive blow”, it is significant. I’d have to agree with you on “tactical blow”.