Fair question - they couldn't even properly maintain the enormous stocks of legacy military equipment the Soviet Union amassed (before the USSR crumbled when it couldn't match the massive spending by the USA).
The trouble with Putin's Kleptocracy is that when you and your buddies steal everything not nailed down, everyone else also gets with the same program.
Endemic theft, fraud and falsification undermines every form of expenditure - even the military 'modernisation' involved more thievery and exaggeration than modernisation.
None of it mattered to them, until now.
After presenting a 'limited, special operation' to decapitate Ukranian leadership and regain control of Ukraine (in 5 days)... Putin has now has a year-long, full-scale war on his hands, with 100s of thousands of casualties, so far, and attacks now even occurring within Russia.
They haven't run out, but I believe Russia lacks the modern materiel reserves that Ukraine can draw upon from its many supporters.
Once upon a time, China would have fronted-up, in some form or another, but guess what?
The ex-commie Putin sympathisers in here seem to have forgotten, but China is communist and Russia is not!
China competes against Russia for influence in Central Asia, and this war is making China look like a more rational partner for them - not to mention its far greater wealth and power.
For all the West's concerns about supply-chains after covid broke out, China also needs the external economic demand only the West generates, and cares not to be subject to crippling sanctions.
Iran's drones, maybe some NK ammo, and the thoughts and prayers of rebel Africans who took power partly due to the old USSR backing them 50 years ago, plus whatever it can get on the black market, is about the extent of it.
Putin thought a long war, culminating in frozen conflict would be second-best outcome, after plan A exploded in his face, but I suspect the present counter-attack will destroy his hold on power.
This is because Russians can choose to fully mobilise and kill the equivalent another couple of MCG's full of their sons, (and Ukranians) and see their National economy hit the toilet where their reputation already sits, or realise the situation can be more cheaply salvaged by replacing Putin.
There is no spin doctor in the West that can allow Putin to keep any Ukranian territory after what has been said about events to date, so it's new Russian leadership, or continued large-scale conflict, in my opinion.
