JWST has at least justified itself with the excellent performance and better than expected predictions for its lifetime (since it is limited by the cooling and station-keeping fuel).
SLS has no such justifications forthcoming. It's too rough of a ride to launch any scientific probes on, it's too expensive for private launch, they can't make them fast enough to do more than 1 launch per year (without pouring more untold billions and decades into it), and the only reason it's even involved in Artemis is because Congress insists on it. Even putting Starship aside, between Falcon Heavy, F9, New Glenn, Vulcan, Neutron and maybe Ariane 6, the West has so much lift capacity available or coming online (mostly drastically cheaper than SLS) that SLS is kind of irrelevant.
SLS has no such justifications forthcoming. It's too rough of a ride to launch any scientific probes on, it's too expensive for private launch, they can't make them fast enough to do more than 1 launch per year (without pouring more untold billions and decades into it), and the only reason it's even involved in Artemis is because Congress insists on it. Even putting Starship aside, between Falcon Heavy, F9, New Glenn, Vulcan, Neutron and maybe Ariane 6, the West has so much lift capacity available or coming online (mostly drastically cheaper than SLS) that SLS is kind of irrelevant.