While I think Harbaugh can be a good NFL coach it is important to recall the specific circumstances of his tenure in SF. The Niners had a good roster that was underperforming. While Harbaugh saved Smith's career, if the Niners didn't have a defensive roster built by Scott McCloughan and coached by Vic Fangio I don't know if they become an instant Super Bowl contender.
Is Justin Fields another Alex Smith? Do the Bears have a trio of all-pros anchoring their defense? Can Harbaugh build a playoff roster?
Is it even that? WR is a pretty low priority. I have to imagine fans would prefer an actual defense or Oline before they start trading for star receivers.