It depends, the Fulmar design was drawn up before the advent of the sort of radio nav aids that made finding the ship 'easy' and with the intention of operating at range from the fleet to hack any shadowing aircraft. In these conditions you need an Observer if you're going to get back to mother in night or bad weather. Although other navies didn't come to this conclusion their area of operations was generally different i.e. the Pacific where bad weather was less of a concern, as evidenced by the open bows on US and Japanese ships of the time.
The Fulmar wasn't intended on countering land based fighters so the performance sacrifice to get the range and crew compliment was less of a concern. As a counterpoint how would the Spitfire have done performing the Fulmar's role on a stormy winter's night in the North Atlantic? It certainly wouldn't have the range and if it did, if the pilot managed to find the carrier again he'd probably write it off on recovery, where the Seafire was useful was defending against land based fighters when the ship was sufficiently close to shore that the navigation issue became moot.
Was the Fulmar a great fighter, no, but then it wasn't a failure either.