But Russia can't maintain it's artillery. The more they shoot their guns the less accurate they become. Having guns that can't put shells on target doesn't do much other than eat logistics.
The attrition is true of any artillery. Including Ukraine's. But Russia has massively more artillery pieces and shells. Ukraine's advantage is that the western weapons are somewhat more accurate and longer range, but not much. Russia is also rumoured to be investing heavily on their own versions of higher accuracy rockets.
Ukraine has access to maintenance. Russia does not have a meaningful ability to maintain their artillery.
Russia is a major industrialized country. Of course they have the ability to maintain their artillery, and manufacture new artillery pieces. Same goes for Ukraine for barrels and such, but the most advanced western weaponry need to be shipped out of the country for maintenance probably, leading to longer delays.
Plus, Russia can hit Ukrainian facilities anytime, but Ukraine can't do it to Russia (except rarely when they get lucky), and Russia is in full-on war economy mode, while Ukraine's backers aren't.
And they do not have a meaningful ability to build high precision weapons of any type at this point--too hard to get the parts.
Not necessarily. Russia has for years been switching to using commercial, off-the-shelf parts for it military equipment to cut costs:
Using standardized, civilian parts means they can be smuggled into the country easily than military-grade hardware. Some time ago Russians got caught
stealing speed cameras in Sweden to be used in Ukraine, for example. I don't think any sanctions regime can block Russia from getting these components through friendly nations. China is probably able to sell them the components they need too.
Can Russia ramp up its production of cruise missiles, ballistic missiles or high-accuracy rocket shells to the level they need to completely crush Ukraine? Probably not. But HIMARS system shows that even a few very accurate strikes can do a lot of damage. Again, Russia is in full-on war production mode and will do whatever it takes to try to bridge the gap between them and NATO.
The longer the war goes on, the stronger Russia is getting in terms of equipment and even manpower... unless its economy completely implodes, but that could take a
very long time. Which is why the west is stupid for thinking that they can win at the current pace.