Russian aircraft industry still remains very capable. It's not unimaginable that they'll be able to keep the planes they stole flying for a while. Sure, there might be crashes like with Iran. But it's not like Russian regime particular cares about the lives of Russian citizens.
Last I checked iPhones were made in China. Sure, Apple might decide not to sell them in Russia but that still leaves perfectly serviceable smartphones from the likes of Xaomi, Huawei and Oppo.
Iran somehow manages to keep pumping oil and gas despite the sanctions.
While there will be obvious loss of productivity, let's stop pretending that the sanctions will somehow grind the Russian economy to a halt or that they will induce regime change.
Engaging in war takes a massive amount of economic production. Especially when your burning resources like Russia is currently. If Russia wants to replace its technology losses in a relatively quick manner it absolutely will take a large portion of their economy to do so.
China itself won't do it, but I forsee that less savoury third parties are probably very interested in partaking this potential highly profitable triangular trade route.
Tu-204? It's performance and efficiency are horrible by Western standards, but it's by no mean bad enough to be unusable.
Irkut MC-21? Most of the actual aircraft don't need to be big to be effective. Russia actually has a small population for it's size.
They actually (well, not anymore) build a substantial ammount of Ukranian aircraft as well, most of the Ukraine Antonov aircraft was more or less actually manufactured in Russia.
