Why do fake Russian accents always sound the same in movies/games/shows, but never sound authentic?

When someone, or the voice of someone is being used, with a fake Russian accent it always sounds awful to me. I’m not sure that I’ve ever heard it done well, but it always sounds like the same accent.
I suspect it may be more noticeable to me, because I come from a family of people with thick Ukrainian accents (which are also poorly done in the media, sounds exactly like the “Russian” accent) and I don’t notice it as much with other accents being portrayed.
Have you noticed something similar with any accent portrayed by actors? Is it a language or accent that you are extremely familiar with? Can you give me an example of someone that you think does an excellent accent, whatever it may be? If you can find me someone that does a great Russian or Ukrainian accent (that isn’t authentic) I’d be thrilled.