Those are irrelevant situations as well as false dichotomies.
How do you go from Rockabilly to Nirvana? Probably by turning down the reverb and adding a ProCo Rat or DS-1? I .... don't understand the question.
Here are some genres that I play on a very regular basis, and since genres are arbitrary, I will name soundalike bands
* Garage-psych (Black Angels)
* "Classic" indie rock (Pavement, Yo La Tengo)
* Post rock (Tortoise)
* Noisy AF Postpunk (Sonic Youth to Psychic TV)
* Alt Country (Sixteen Horsepower, Townes Van Zandt)
* Weird krautrock - dub stuff (Cabaret Voltaire, early Ministry)
* Odd semi-classical instrumentals (Vini Reilly is a reference, though I can't sound like him)
* Shoegaze (Ride, Slowdive)
* A lot of different EDM-ish stuff with a Big Beat emphasis (Fatboy Slim, U.N.K.L.E.)
And that's just personally - I may go for months without hitting one of those, but it's always a possibility. I also record the kids at school, everything from Adele to Djent to Black Metal.
I am busy, I work from 6:50 a.m. t0 2:40, and then there's grading and about 12 hours a week of outside of school stuff.
If someone came along and said "hey, I know it ain't your thing, but want to do some reggae covers of the Eagles?" I might say 'yes.' I might not. But doing so has nothing to do with whether or not I pursue my interest in the list above.