What was it about Nirvana that was so innovative?!

What was it about Nirvana that was so innovative?

Don't give me a hard time. I am as old as dirt.
Thanks

Because right before Nirvana became huge, all the big rock groups at that time had the big teased hair, wore makeup, wore fancy outfits...and they all had these huge egos and wrote songs about how cool it is to be a famous rockstar who partys and gets laid all the time.

Then this group Nirvana comes along, wearing nothing but jeans and flannel shirts. They didn't wear fancy clothes, have fancy hair, or brag about being rich and famous. They were real guys singing about real problems. They spoke to millions of teenagers who were depressed and trying to find something to relate to. Nirvana did something completely unlike anything that was popular at the time, and their originality was rewarded. They became the biggest band in the country. Fellow groups like Alice In Chains, Pearl Jam, Soundgarden and Smashing Pumpkins were getting heard now to. But Nirvana wasn't just in the right place at the right time. The lyrics were brilliant and insightful, the music was original and different, and their anti-pop / anti-fame attitude won them over with fans even more. Personally, I don't see how someone could listen to the "Nevermind" or "In Utero" albums and not find them brilliant. Nirvana's sound was often immitated, but never duplicated, and I think Kurt Cobain was the John Lennon of the 90's.