Su-57 is sort of like Sputnik V. The results are good. The performance is promising. But it don't have the manufacturing capacity to make any real world difference, nor does Russia have any meaningful global soft power to sell it.
Russia's attitude to this is that they don't need so many units of Su-57. Whatever an individual chooses to believe, this is still objectively true. They do need to be more sensible on their budget like everyone else who doesn't print money and put a gun on everyone's head to dictate how much their money is worth and what and who they can and can't trade with.
Russia's per capita income compared to China is nominally higher but their overall available budget is much smaller. 1400 million people compared to 150 million. China's metrics are also scaled down due to purchasing power plus devalued RMB. If RMB is allowed true value, China's economic size (a 1 dimensional measurement) basically doubles along with RMB.
Pouring billions into expanding production lines so Russia can get Su-57 up to some ideal form and mass produce them isn't quite a viable strategy. For potential show downs on borders or proxy wars, they require a well equipped conventional force of certain volume. I believe they have that. It is much less a question of capability or available wealth when it comes to the production of the fighter. If they get some export orders of volume, it may become worth expanding production.
Russia can't employ some sort of T-34 attitude to modern fighters without going broke. No one except the US can. So why engage in a losing fight? China building J-20s cannot match F-35 production rate but it is necessary in case the region goes into war. The Americans can only bring over so many F-35s and F-22s before their airfields and carriers are attacked and destroyed. With Russia, any attack on it could unleash too much of a risky gambit for Europe. Do you want to try your luck with tens of thousands of Russia tanks sweeping through? Or better not poke that hornets nest. If Russia loses, get ready for thousands of nukes. You cannot win so there is no fighting or waging real war on Russia. Playing psyops and trade wars is all they will risk. With China, the western powers don't actually care what happens to Asia or their major allies there because they don't live there and barely have investments around compared to Europe. Which is why China actually does require both a nuclear or WMD MAD guarantee
AND have a conventional force that can resist. Until the day China has MAD several times over, the conventional necessity is there, particularly with regards to proxies and smaller conflicts that may arise.
Russia can choose to lower capability and quality by going faster with Su-57 or pour a lot more resources into it. Both would be relatively unnecessary compared to China with J-20.