Yeah those are good defense systems. But I think the idea that they could invade NATO is unfounded. I'm armchairing but while I do think they have some very good weapons that seems impossible to me. I do really like their engineering and I do believe Russia is treated unfairly and that we should try to be their allies to counter China.
Post Cold-War we were allies with Russia and ran joint military drills and operations with them for a time. That should have never stopped. We kicked them into being close allies with China, which is not good. Chinese engineering has always been poor unless they steal technology, but they make a lot of it (see their retard massive failing Navy). The Russians have always been good at making good tech, but not having means to produce it. Dangerous combo
russia doesn't have a good air force at all. they specialized in air defense because they knew they would be worthless against NATO. the S400/S500 are amazing pieces of technology that should not be dismissed