Well, first and foremost, possession and even use of the Darksaber doesn’t mean that the user is Force-sensitive.
While most instances of lightsaber use in Star Wars have involved Jedi, Sith, and individuals later kinda sorta confirmed to be Force-sensitive, the Darksaber has almost exclusively been wielded like a sword that just happens to be powered by a kyber crystal, rather than the weapon of a Force-using warrior.
Moff Gideon doesn’t have to be able to use the Force to use the Darksaber, which is good news for Mando and Baby Yoda.