First of all, I would say you don't have to feel embarrassed for thinking like this. I would say it's normal for every aspiring artist to think like this at some point in their life, meaning "oh no, X artist is clearly a genius and I'm shit, I'll never be able to be like him/her, might as well just give up now!" It's normal, and it shouldn't discourage you from seeking your passion, be it writing or anything else.
Second of all, and this is something MJP mentioned somewhere, the term "genius" is vastly overused. It should probably only be applied to people who come up with new revolutionary inventions or concepts (think of Tesla or Marie Curie). Even then, I think the term could be used more sparingly. Sure Bukowski, Van Gogh and John Lennon were all great artists, but they weren't "geniuses." They were people who spoke from their hearts about things that rang true to them. They were honest and weren't afraid of doing something different. That's what made them special. Sure they may have been a little talented to start with, but they weren't godlike creatures with comic book levels of intellect.
Third thing, take off your rose-colored glasses. I can relate because I used to think like that when I was a young teen, but it's seriously dumb and even dangerous (as evidenced by certain figures that have recently risen to power) to think like this, meaning "WOW! Nirvana, so cool! Too bad they don't make music like this anymore! Wish we could go back to the good old days." Many of the themes and issues Bukowski wrote about are still a thing today. Extreme poverty, abuse, discrimination, addiction, sexuality, classical music, etc. Plus, now you have a lot of other stuff to write about! This includes but is not limited to: surveillance, terrorism, videogames, dating sites, internet forums, among others. You could write a story about how you got drunk and went on a ramble on a small internet forum before calling your ex and going to her house to watch Netflix while also receiving a message from a racist internet troll that sent you on a goose chase. Also, I doubt Bukowski was a fan of his generation, either, from what he has written.
Last but not least, keep going, man! Don't get too stressed about it. Writing comes when you least expect it. Two months ago I was writing some of the best things I've written, but since then I haven't written anything to save my life. Yet, I've been working on myself in other aspects or just outright letting go and enjoying the moment. Life is too short to worry about a single thing for too long. I'm sure Bukowski would agree.