You can’t fight a modern war for 3-4 years with all the financial investment needed and not see your economy tank.
Russias GDP before the war started was less than the UK and on a par with Italy. Without oil and gas they’d be stuffed already, that’s what’s kept them going.
They moved to a low-tech manufacturing policy on the back of going all in on arms production. So even the tanks, aircraft and other military vehicles that are being mass produced are mostly without modern tech. Likewise their civilian manufacturing has followed the same low-tech path.
They’ve muddled through up to now but if they keep the war going then their economy will break for sure.
Yet they regularly use hypersonics, and just live field tested a system beyond anything the US has.
Not to mention the current drone technology using fibre optic guidance.
Not to mention AA systems and aircraft.
Tanks and BMPs have always been designed as low tech compared to the west, it's partly why they can churn out a stupendous amount in comparison, and looking at the performance of the Abrams and Bradley they blow up just the same but take ten times longer to build and train on
Low tech like the FAB guidance modules seems to work fine though.