While I appreciate the sentiment of avoiding unnecessary cycling accessories, I can't help but raise an eyebrow at the assumption that everything on the market is just marketing hype. I mean, sure, there are plenty of frivolous gadgets out there, but let's not throw the baby out with the bathwater.
As for the most unnecessary accessory, I'd have to go with those fancy carbon fiber water bottle cages. I mean, seriously, who needs to spend $100 on a bottle holder? A simple wire cage from the local bike shop will do just fine.
But let's not forget that practicality and functionality don't always have to be at odds with aesthetics. Sometimes, a trendy gadget can serve a useful purpose. Take bike lights, for example. Sure, some of them may be overpriced and overhyped, but a good set of lights can make all the difference when it comes to safety.
As for educating the masses, I think the key is to approach each accessory with a critical eye and a healthy dose of skepticism. Don't be swayed by flashy marketing campaigns, and always ask yourself if the accessory in question is truly necessary for your cycling needs.
And if all else fails, remember the words of the great Thoreau: "Beware of all enterprises that require new clothes." The same goes for bikes and accessories. Stick to what you need, and you'll be just fine.