Heinlein's sci fi didn't age well, because it was written for juveniles and then later his social ideas overtook his sci fi ones.

He had the same blind spots that Ayn Rand did, but perhaps better informed of the fascist-adjacent US culture.

One of the good sci fi/social ideas he had was about what it meant to "grok" something. groklaw.net of happy memory was exactly what that verb was supposed to mean, dive into something until you understand it at a molecular level.

The fact that Musk et al have stolen terms like "grok" and even "cyberspace" as if they own them is something I loathe.