As far as I know the US military still has more 4gen jets than 5gen.
Obviously Russia has no 5gen at all (or just a few 5gen Su-57, if we going to name them 5gen).
Anyway, my point is that as of now Russia has no need for gen5 and can't afford it anyway, just like about anyone else except for the US and a few countries that have them but at the same time have to rely on the US anyway.
I don't have access to perfect information, but I find the reports that Russia is unable to maintain their entire fleet creditable, and believe and/or the experts who confirm this analysis.