I think this can work only if we as customer also learn to cross examine his reasoning and ask hard pointed questions.
Once an advisor is acting as your fiduciary, it's not lawful for them to advise you to do anything but what is in your best interest. Further, they may not have any conflicts of interest. This was supposed to be the case for all US retirement accounts, but the Financial Services Industry fought tooth and nail to defeat the Obama era rule.
Competence is a qualitatively different problem and has different solutions. Usually, one would look for past experience, performance, and educational credentials to gauge competence in those they hire.
I do agree that the more educated client, the better. But, personally, I can only have domain expertise in so many areas, and I only have so much time. Outsourcing is a logical strategy.
I do think that there are some firms, who cater to mostly very wealthy clients, who can consistently beat the market, or at least have a good chance of finding some niche or anomaly every few years for a huge jackpot such that their overall average is higher than the indexes.
The problem is that most of us won't have access to these people.
Instead, our professional is going to be the typical financial planner who has far less of an understanding of math than even the typical CS / engineer grad, and is basically a commissioned sales person who will take 5% off the top, plus another 2% a year - all for basically investing it in the same index funds you can now buy yourself with a Schwab or Vanguard account.