The franchise has run out of steam, not because spy thrillers have played out, but because the thought of an individual risking his life, "for king/queen and country," is little more than a quaint anachronism, when the UK has opened its arms to its worst enemies.
The best bet for the franchise at this point is to go retro with an origin story showing Bond's coming of age in WWII and early cold war exploits.
I never saw any of the Bond films with Lazenby or Dalton, so I really can’t judge. When you get right down to it, I haven’t seen many James Bond movies at all, not even all of the Sean Connery ones. The last Bond movie I saw starred Roger Moore, whichever one had the spiral car jump in it. Always preferred the books, and it’s been a long time since I’ve even read any of them.