I'm not fond of ketchup. I use tomato paste when I make Thousand Island dressing. I also use relish that isn't sweet. If I can't find any, I finely chop some dill pickle. The dressing is not nearly as sweet that way. I will sub tomato paste for the ketchup in Russian dressing, if I ever make any....
See, guys, you actually have to like Russian or Thousand Island dressing to want to use it. I. Hate. Ketchup. My one odd exception? Cold meatloaf sandwiches. To each his own, though, so if you enjoy it, have at it! ~ And gobs of any condiment ruins a well-made sandwich. All things in prportion, please, and nothing in excess...unless it's bacon. One can never have TOO much bacon - unless they don't like it to begin with.