The other issue is that the Russians prefer packaging the munitions. There's basically no room for custom integration work -- either the Russians don't want it, or it's high risk/cost (see India's MKI issues).
While the Chinese aren't any different, we can at least tap into our existing inventory of SD-10, C-802s and REKs for the J-10CE, hence reduce some of the added cost. With the Flanker, it'd be an entirely different and drawn-out procurement scheme.
And there's CAATSA too, of course.
IMHO the only realistic approach with the Russians is to try paying them for expertise. That's the only way the Russians are going to get past CAATSA, so they'll need to evolve their business model from selling hardware to helping others develop IP across critical areas.