Funny you should say that, on my local park lake it was 3 grains of corn held up by a single piece of fake corn over Vitalin that produced the vast majority of the carp caught. It is a very silty lake and most people tended to fish boilies which sunk into the gunk. The Vitalin and sweetcorn sat on top. I had some very successful sessions, and watched many others fail to catch.
Boilies did work, but only in specific places where the bottom is slightly harder.
I think there were or are some specials that really work, but I think many have changed as flavours have been regulated. The Solar Squid and Octopus, original Scopex (not later copies), Monster Crab, Green Zing, or Pineapple really did have something about them, there are still others now that work, but is is finding them.
Add to that, fishing over bait whether groundbait, particles or beds of boilies may make our 'non smelly' baits effective, or even the single bait that the carp think 'here's one I missed earlier'.