The Russians aren't in a great rush to acquire anything new because they're simply short of cash. People seem to forget that Russia's GDP is about the same size as Italy. After they pay for their strategic nuclear forces there's not much room in the budget for anything else.
Sure, but they do have a healthy export market for their armaments...
Russia's remaining arms customers are mostly poor and desperate. They can't afford 5G aircraft. India used to be a major customer but now that they have more money they're shifting purchases to better alternatives.
The F117 was 70's tech. It looked like a weird polyhedron because we didn't have good enough computers to do the math on how the shape of a plane reflects radar. And it was only shot down because the bomb bay doors weren't stealthy.
Given that was nearly twenty years ago and we've since had massive advances in passive and synthetic aperture radar otherwise, I've long wondered about the worth of the massive extra cost stealth brings to Fifth Generation warplanes.
Given the Russians don't appear to be in a great rush to make all their wares stealthy, one wonders whether they've preëmpted its limited use in future?