The prequels have done enough to ruin ObiWan as a character, making him incredibly wooden and boring, we don't need Disney making things worse. Do all of these characters need to be milked until they're utterly unlikeable and you forget why you were even a fan of this stuff? The young Han Solo movie on the way is already a nightmare.
Yeah, tbh I thought McGregor was a total snore as Ben - not necessarily his fault I guess. Seemed to get lost in the impression of Guinness and the terrible dialog.
Prequel versions of characters are usually doomed, but there are movies like Godfather II that do it well by setting up a really urgent new story world around the younger character - the PT really had none of that though.
I do think part of it was McGregor though - he plays intense/edgy really well (Trainspotting) but is quite bland in straighter fare (Salmon Fishing, Tsunami movie) and his star has waned in the past decade. Not sure Disney would bank on him, and also him playing a role from a Prequel, a trilogy they seem to working hard to ignore.