Trump doesn't have the authority to create new federal agencies, so he claims to have repurposed the authority of an existing one, retaining only the shell for appearances. I don't think that can possibly be constitutional - it entirely defeats the point of Congress having that authority, and is effectively a line-item veto if the law can say "this agency will exist for X purpose" and the president can simply ignore the "for X purpose" - but it doesn't matter if neither Congress nor the courts are willing to do anything about it.
For me, the only charitable interpretation of DOGE is that they have accidentally figured out how to spread incompetence (not wholly unfamiliar to much of the government) to the small islands that fended it off (gutting 18F/USDS). The cherry was accidentally firing a chunk of the nation's nuclear experts to save a dime, and then clawing them back.
I think any claim of DOGE doing good work has to address those things in a convincing manner (in addition to why the existing processes are lacking; GAO). I haven't seen that attempted by anyone.