There are many misinformation out there, but this much seems to be true.
From
Wi-Fi Security Flaw Not As Bad As It’s KRACKed Up To Be:
Conversations with a few security experts made it clear that while the Wi-Fi access point side of the equation isn’t at fault for these negotiation flaws, even consumer-scale access points could be updated to block, resist, or report KRACKs. (There’s one exception: corporate-scale access points that support “fast handoff” act a little bit like a client in that mode, and routers with that feature have to be patched, too.)
So while it's the client devices themselves that are at risk (unless multiple routers are meshed with fast handoff, aka 802.11r), a good router can prevent KRACK altogether.
AirPort Extreme and Time Capsule are not prone to KRACK themselves. But it is not known whether they can resist KRACK from affecting unpatched client devices.