But war is something you do not plan many times , it just Happens.. . Look at Georgia war in 2008.. did Russia planned that war? No.. it just happened and they had no choice but to send tanks without proper protection
and get more casualties . And now you have Ukraine.. that are already the radicals bombing Russian territory.. with casualties.. If they start a major genocide ,lets say they bomb Donetsk/Lugansk Chemical industrial Plants it will create a major catastrophe with thousands of civilians killed and probably with RUssia territory also affected forcing Russia to invade to restore order.. not as a planned thing but as a unplanned one..
So it make no sense why Russia do not use Arena at least on their T-90 tanks.. Today more than ever Tanks will be a more important weapon for Russia even than SUbmarine or warships because of a major war happening in their borders. ,that at any time they could be forced to just like in georgia Invade.
leaving their T-90 tanks totally unarmed from arena active protection is a really bad choice.. because their Armata will no see action for a least 3 to 5 years in a real war. until they manage to sell it first in enough numbers. It will be ugly if NATO send top attack anti tank weapons in the thousands to Ukraine and they are forced to invade with no defense against top attack weapon .
The chance of a war with Russia is low because even a primary schooler with normal IQ can understand that Russia is a massive country with huge military/industrial system with no nearby country can rival. And it has nuclear weapons.
Even without T-90 Russia can easily swarm the battlefield with thousands of older tanks which easily overwhelmed the enemy. If aiming for a favourable treaty with little or no territorial change for both sides, it would be an easy win for Moskva.
You have already seen how Moskva took back Krym and liberated Ossetia and the West can do nothing beside the meaningless "sanction".
Furthermore, people have already seen the true "color" of the so-called colorful "revolutions". Except the facist scums in Kyiv.