At least SpaceX figured out a few years back that a LOx- RP1 upper stage was a non-starter for heavy GEO missions. The Isp trade-off between LOx-LH2 and LOx-RP1 is huge.
Unfortunately, Rocketdyne kind of screwed the pooch back in the 80s with a poorly designed injector on an unstable LOx-Methane engine. To their credit, companies like XCOR and SpaceX have figured out that methane was not the bad actor, rather the poorly designed injector. Took ‘em long enough.
XCOR Methane Rocket static test
https://www.youtube.com/watch?v=dumolLDfWw4
(crank up the speakers for this one.)
LOX/LH2 does have a better Isp than LOX/RP-1 but you run into more complications using LH2 such as metal embrittlement because it is so much colder than most cryogenic fluids. So it was a tradeoff they thought would work for them.
But SpaceX figured out how to handle methane plus they are tackling the closed combustion cycle increasing thrust significantly.