Dude, our private companies like Kalyani, Tata, L&T etc are building cutting edge weapon systems and and we have become self reliant in lot of key technologies. And as for the later part, f35 is for real while j20 is a hoax. It's just like you buy a cheap Chinese copy of an apple smartphone which looks exactly the same but when you use them you get to know the difference.
Even russian have not been able to build q decent stealth fighter. Su57s stealth capabilities are questionable and its engines are underpowered, this is the reason why India walked out of that program.
Most of the Chinese weapons are but knockoffs of the russian weapon systems. When russian themselves haven't been able to do it then how can Chinese be expected to do so when they themselves copy russian weapons?