Top Gun, Days Of Thunder, Crimson Tide, Spy Game, although certainly not Oscar Worthy, are considered good films. Enemy of the State, Man on Fire and True Romance are films that have also been reasonably acclaimed. As you have pointed out, Scott's films aren't known for their profound substance, Tony Scott is known for his visual flare. Which has always been a strongpoint in the Bond series.
The fact that Tamahori was a (debatebly) renowned director was not the reason Die Another Day failed. DAD failed because of Wade and Purvis' ridiculous and childish script, along with EON's inane willingness to make the 20th Bond film some sort of 2 hour homage to the rest of the series that bordered on self parody and Tamahori's (and EON's) decision to try and make this Bond the biggest of them all, without any regard for substance or story.
Brocolli's regard for unknown directors has more to do with ego and artistic control than it has to do with maintaining some level of artistic quality. Considering Spielberg directed Raiders of the Lost Ark, which absolutely trumps any Bond film from the 80's and most of the rest of the series, I'd say it was Brocolli's stubborness to compromise which lead to his desire for unknown directors. While, Spielberg ruled the movie universe, Brocolli gave us John Glen, who directed many Bond films in the style of a made for TV movie.
Luckily, Brocolli and EON have always had brilliant actors to save the films from the mediocrity of recycled plots and tired action scenes. If Barbara and Michael G. can escape from Cubby's approach to the Bond franchise and learn from their mistakes during Brosnan's tenure and continue their success with Craig and Casino Royale, Bond fans will be in for one hell of a ride.