I would rather upgrade T-72/80. The important thing would be to have a large number of tanks with a reasonable amount of modern technology: thermal sight and BMS if funding allows. Other improvements that T-90 offers are secondary in my opinion (engine, better ammo, armour...).
The main problem is numbers. The size of the military has been greatly reduced and when you have fewer chess pieces to play with... you give up the pawns first.
The new Brigades will not be cheap, and the shift of some units back to divisions might reflect that.
A brigade structure is a more mobile but smaller force that takes everything it needs with it. Short and simplified logistics chains are very important for such beasts.
For a divisional structure you are talking about a much bigger group, though savings in logistics will also have an impact it will never be as mobile as a brigade.
Taking a brigade from a division will not be the same as many of the support elements will be part of the brigade and will need to be allocated separately.
I do agree that for the moment night fighting ability and C4IR are much more important as armour and mobility are already pretty good and adding new ERA should be fairly straight forward and cheap anyway.
This means thermals and BMS are the focus though new ammo can also be introduced too... no point producing old ammo when new ammo is better.
Ideally however further upgrades to T-90s with electronics and equipment designed for armata makes a lot of sense in terms of commonality and production numbers.
Russia should have de develop, and upgrade its flying tanks like Mil 24 beside, Mil 28, and ka 50, these are future of battlefield.
They are... but a helo cannot replace a tank and vice versa.
A tank is a well armoured ground vehicle that can support troops and hold ground. It needs a big powerful gun, excellent optics and good armour.
I rather suspect the later model armata MBTs will operate by remote control in very dangerous areas... making them very hard nuts to crack.
You can argue by the same logic that you can withdraw all aircraft because S-400 exists.
The key is to correctly analyse your enemy and also the strengths and weaknesses of your own equipment and use tactics to maximise the strengths and minimise or eliminate the weaknesses.
For instance Javelin and Kornet are described as the end of tanks, yet a good DIRCM or effective IR signature reduction would defeat Javelin, while Kornet can be defended against using APS.