That's exactly what happens. But not out of ignorance and not only in IT. It's recipe for marketing success in any domain. Customers only know the problems of c

That's exactly what happens. But not out of ignorance and not only in IT. It's recipe for marketing success in any domain. Customers only know the problems of current solutions. Solve those and you get instant influx of customers. Sure, your solution brings it's own problems but it will take a very long time for them to surface and become common knowledge. First people will only check that your solution does fix the old problems in testing environments. And it does, so they move on. When they encounter implementation/production issues that's actually an opportunity for you to sell consulting. People who took the bait early on will mob on any naysayer: "Agile doesn't suck. it's just most implementations, but real Agile rocks!"