But the argument here is not that they'll have to make do with lower quality parts. It's that they won't be able to get or make the parts they need at all. That is a very different and much less likely argument, especially as there are still many countries they're trading with through which imports can be routed.
No, today it's the same. They're thousands of miles away from today's precision manufacturing. They won't be able to make usable parts. If they try to use whatever they produce, their machines will likely explode, or at least grind to halt.
So then they'll buy more parts from their friends in Germany? After all, they have to sell the Russians something in return for all that gas.
I think you are seriously over-estimating what sanctions can do. Even if some Russian machines do explode, much harsher sanctions have routinely failed elsewhere. It'd be nice if this is all it took to end the war but it seems unrealistic to assume so.
Where is that elsewhere? I visited some sanctioned places and it was as I said here - yeah they make some stuff, and all of it is shit, doesn't work at all, or breaks down very soon. There's a reason why there's a car repair shop at every corner in Iran.
And their "friends" like China won't ever let them have the machines that produce machines, because that's how they dominate others (and China learned that well from the West).
A good part of Chinese high tech factory machines are made in places like Germany [1]. This is slowly changing though as China is becoming a major exporter of production machinery themselves, albeit starting from the low tech side of things (think plastic molding).
