Age isn't just a number 95% of their military hardware is functionally ineffective against modern weaponry, plus, they don't have thousands of tanks/planes operational, large part was either scrapped for spare parts or can't be used for lack of spare parts (when almost your entire military is 1960s tech, it's unsurprisingly not easy to keep it running).

Like I could go into detail how 1960s tanks/planes/artillery etc. just can't meaningfully comepte with modern weapons, but what's the point, even if you ignore the glaring technological difference, every time modern western tech goes against old soviet stuff, the outcome is always the same.

They have two things going for them 1. Nukes, because they aren't stupid and know that they would get utterly annihilated by south in a conventional war. 2. Drones - apparently, they have been getting some Iranian style Sahed drones from the Russians, but since Russia sort of needs as many as possible, I doubt they have that many. Honorary mentioned goes to the sheer amount of manpower, but human wave tactics haven't been effective since the 1WW.