The Su-57 definitely isn't at a disadvantage compared to the F-35. Also, let's face it, Russia hardly projects power. Any conflict with the west would likely be the US attacking Russia. Hence why Russia is putting so much effort into systems like the S-500.
The US has invaded and occupied several countries on the other side of the world in the last few decades. Russia's conflicts have been limited to their periphery and Syria, where they've always had a base.
"Russia invades neighbors" is worse, as they intend to occupy and annex. America invades with some idiot idea of democracy or projecting hard power, only to leave.
Russia invaded far off lands when they had the capacity, don't think they wouldn't do it again if their economy and population weren't shrinking.
There is actually real serious money for it - India has been wanting to buy a fleet of those planes for years and is pretty frustrated with the delay. Russia still is just not capable of producing it. Too complex tech.
Specifically the 3 major components has to be of the 5th generation - body, engine and radar. The SU-57 body is pretty much there. The radar isn't there yet where it was promised and is required to be (ie. distance, number of tracked items, etc.). The worst situation is with the engine. Russia still doesn't have 5th gen "stealth" engine. What is being flown currently is "4.5" gen - a well improved 4th. You can see it clearly here https://en.wikipedia.org/wiki/File:Sukhoi_T-50_Maksimov.jpg
