The problem with SLS/Orion is that they make manned exploration of space much less likely than if they didn't exist at all. These once off yearly mission to anywhere that doesn't require a lander at a cost of at least $3-$4 billion a pop if maintenance etc is included ensure that NASA will not be developing the technologies that can be game changers like SEP,NEP, life support systems and Habitats for Mars,moon etc.
You're assuming that if SLS/Orion didn't exist, some of that money would go into developing "game changing" technologies, which would make future missions much cheaper. First of all, there is no guarantee that money would be spent on "game changing" technologies or that the technologies would be "game changing". That's what the previous administration tried to do and it failed completely at the political level.
I believe the way forward is to use existing technologies to establish Lunar and Mars bases. That will identify which technologies are needed most for future advancement. This is much like how the ISS established a need for cargo and crew transportation to the ISS.
I actually believe if the money was used to gold plate all the public toilet seats in North America it would be better spent. Because then NASA would have to buy innovative solutions at best possible price for service which means we would end up with probably at least a partially reusable system which could launch something similar to the orions capabilities for $200 mill a shot rather $3-4 billion. We may Evan end up something like ITS for half the development cost of SLS
Just imagine ITS 450 tonnes on Mars development cost (lets say $ 20 bill x2 Elons estimate)reusable many times versus SLS zero tonnes on Mars for $30 billion and nothing reusable.
I would much rather they tried and failed at ITS than spend next years running a poor imitation of Apollo.