MSR has indeed been a mess. I think it's pretty obvious that NASA has been trying to instill a "sunk costs" mentality in Congress, and it's not working out the way they wanted.

MSR is a fine enough concept though, I think Rocket Lab's proposal to get it done is sound and the government should take them up on the offer. If nothing else, the money to Rocket Lab for MSR development would help to make Rocket Lab a more viable SpaceX competitor, which should pay off for the US government in the long run.