What have skeptics contributed? Logical methods for one. Critical thinking principals as a second. Skeptical thinkers developed and improved on many of these thought processes that are now the basis for reasoning. Though sometimes it's hard to tell.
Look at the helio-centric model... Look at the particle-wave theory, look at ball-lightning. These were discoveries made out of skeptical acts, because someone, or several people doubted current scientific understanding. They traversed significant hurdles often spending decades to try to prove their theories were correct.
You are taking your frustration with the modern scientific skeptic out on skeptics across all time and space. Skeptics were the drivers of logic and reasoning "back in the day." Modern skepticism or "scientific skepticism" is a joke. It is no way similar with classical skeptical practices.