You cannot just wave your hand and say SpaceX. As much as I think it's the better option to use falcon heavy, it's not ready this week.
Nobody says this first SLS shouldn't launch. Not that it would matter much if it didn't, but still.
The discussion is about forward looking space policy for the next 10 years, for the whole Artemis program.
SLS will fly LITERALLY 1 and then not again for 2-4 years. In that time a strategy change can and should be made.
If it fails, there’s a good chance those billions will redirected into in actually sustainable launch system.
It does suck to want something to fail, but you have to think about the bigger picture here and the greater good. No one is going to die.