Ranch: fine in certain situations (chicken/bacon/ranch pizza is great), OK as a veggie dip, should be illegal as a salad dressing, often bleu cheese is just a better choice when it could be used.
Mayo: good on fries and in burgers, excellent in but not the only option for deli sandwiches
Ketchup: 90% of it tastes like overly sugary shit, good ketchup is fine with fries though, best use is with meat loaf recipies/as a sort of glaze on top of meat loaf IMO, overused like crazy, easily replaced or made unnecessary
Mustard: use cases vary based on type of mustard, can be good with Italian meats, or on a burger, almost mandatory on a hot dog IMO, other types have use with things like egg rolls
All have uses, but if you're the type who says "I put ketchup/ranch on everything", you have no taste.
"That is why war is so tragic. To win means to make victims of your opponents and give birth to hatred." - Kratos Aurion, Tales of Symphonia