The "experts" wrt the economy are more "best guessers" than is the case for dentists and doctors because the markets are more chaotic. It's changes with public confidence for one thing, no one can get a good handle on that or every investor would be a billionaire and there would be no one who lost their shirt. We all know the consequential, wildly incorrect forecasts made by "experts" in the past.
Brokers aren't called brokers for nothing, They invest your money until you are broke !
Plus we are aware that if you put your favourite assumptions into whatever calculations you make, you tend to get the answer you desire.
I think the lack of respect for "expert" opinion is probably based on that past experience and the suspicion of hidden agendas, either making it easier for the "expert" if change can be avoided, or a desire to boost official Government policy.