They did keep referencing it through the Moore era - watch the scene in Spy Who Loved Me where a single reference to her death makes Bond pale. And not how Moore's Bond goes fucking apeshit whenever a bad guy threatens a woman.
Lazenby seems like a decent enough chap, but OHMSS (a decent enough film lifted up by the awesome Diana Rigg, oh yes!!!) is pretty solid proof he couldn't act for toffee, and him quitting the role (or getting sacked, depending who you listen to) is a fairly big reason the Bond films didn't die out in the 70s. (I know the joke was Roger Moore couldn't act either, but that's rubbish - he had a very sparse acting style but he's very good at repressed middle aged stuff in films like The Man Who Haunted Himself. Although I would say that, he's my favourite Bond.)