They dropped the ball on Blofeld.
Charles Gray was a good choice to play Blofeld, but damn this film screwed the character up.
James Bond has thwarted numerous SPECTRE plots, he's killed several of their agents, and he's escaped capture at the hands of Blofeld on more than one occasion. Meanwhile, Blofeld is the terrorist mastermind responsible for the death of Bond's wife. These two should should be inclined to kill each other on sight, but instead, either man seems to have only a passing regard for the other or what they're capable of. I know that they needed to keep Bond alive, but there is no reason why Blofeld wouldn't have shot Bond on sight. Bond burned a Blofeld double alive in the pre-credit opener and will stop at nothing to kill the real one. But instead, Blofeld explains his plans, puts 007 on an elevator, and has his henchmen place him in an unfinished pipeline in the hopes that no one will notice him until it's too late. What? Was he worried about getting blood on the carpet? It's not his carpet! It's Willard Whyte's.
But the absolute worst part of the film, for me anyway, was the anticlimactic finish. Bond and Blofeld were supposed to have a submarine chase which built to a fight to the death inside of a salt mine. That is awesome, but unfortunately they didn't have the money for it. So instead, Bond knocked out the crane operator and smacked Blofeld against a wall while he was trapped in a mini-sub. He never even identified himself as Blofeld's attacker. It's an off-screen "death" which was obviously meant to set up to another film, but then EON lost the rights to the character. And even if they hadn't, they really needed to end the Bond/Blofeld rivalry here.
This movie was just such a waste of potential.