Mueller didn’t half ass anything. He conducted his investigation and determined that crimes were likely committed, but that he didn’t have the power to bring charges in his position as special counsel and it would be up to the AG.
Which is true. A DOJ special counsel is not the same thing as the independent counsel that used to exist, which was what Ken Starr was when he investigated Clinton.
A DOJ special counsel is completely beholden to the AG and DOJ policies and can’t bring charges without the AG signing off on them.
If you actually read the mueller report, it’s extremely damning and he turned it over to the AG and Congress to do something about it. The AG declined to bring any charges based on a DOJ memorandum that says a sitting POTUS cannot be charged. The House impeached Trump over the findings and the Senate failed to convict and remove him.
The current AG could still bring criminal charges over the conclusion of the report, but at this point it’s been so highly politicized that it would be impossible to get a conviction on.