Huge difference between the small delta boosters (except for heavy) and giant STS/SLS segmented SRBs.
Delta never carried people either.
Exactly. Delta-IV Heavy is hydrogen all the way from surface to GEO.
But we're getting away from the fundamental issue, here.
We've been using LH2 extensively for decades, in all stages of launch vehicles. We have decades of experience handling LH2 safely and efficiently, with little to no drama. LH2 is not some new or exotic rocket fuel that should be difficult and scary. It's old hat. VERY old hat.
That raises a question that demands an answer: What in Heaven's Name is going on with SLS??? ULA has no trouble handling large amounts of LH2 with Delta-IV Heavy. Arianespace has no trouble handling large amounts of LH2 with Ariane 5. NASA had no trouble handling large amounts of LH2 with the Shuttle/STS, or with Saturn V.
Why can't the SLS team manage it?
I submit that the answer is gross incompetence and stupidity at the highest levels of NASA, with trickle-down effects into the design, construction, and operation environments. And it started with gross ignorance, arrogance, incompetence, and stupidity in Congress.