Take, for example, an electronics or hardware project. The majority is a bunch of experienced engineers who will tell you that your project will take years based on their own experience with an earlier project. What they neglect to account for is that their earlier project took years because of the state of the art at the time. They're taking experience that applies to the era of NAND flash and board bring-up and applying it to the era of eMMC and main-line Linux drivers. So while their estimate is very conservative, it is also very wrong and you should take it with a grain of salt.
Any judgement that relies on some external context, like the industry state of the art, can no longer be trusted in a different context.
The hardest part of talking with experts is to make sure they answer the same question as you want answered.
"How quickly can we get something that more or less works for a demo?" is very different from "When will this be ready for mass production?" They can't read your mind and often to consider context you are not even aware of.
There is also a bit on the what question are people answering, aspect. How long will it take to take pretty much any electronic product to production? Quite a while. How long would it take you to build a prototype that you can play with? Probably not long at all.
Any judgement that relies on some external context, like the industry state of the art, can no longer be trusted in a different context.