The 'state of the art' that SpaceX is pushing is nearly entirely a software thing aided by Falcon's unique engine arrangement. Hardware-wise Falcons are no more advanced than an SLS core stage, and are likely even ore technically primitive than most LVs. If SLS' mission criteria included an emphasis on reusability, NASA would have a fully reusable booster + core stage by now.

This decision was entirely due to doctrine. STS was designed as a mostly reusable product and failed costs-wise, so the government basically forced NASA to go with something expendable instead. It is genuinely impressive that SpaceX proved that reusable launch vehicles can be made cost-effective, but it's nowhere near the kind of massive quantum leap that SpaceX's legion of hardcore followers seems to be convinced it is. Everything on a Falcon or a Dragon is public domain 60s technology besides the code and guidance hardware (based on COTS components). The same is likely be true of Starship, which explains a lot of the significant teething issues it has suffered over the past several flight tests.