You are right, that politicians should decide what is in our best interest. That is the problem though, they aren't picking what is in our best interest. They are picking what is in their best interests.
If you go to countries with a parliamentary democracy, they already show more promise about doing what is legitimately beneficial to their own citizens as compared to the US.
In Canada or Sweden, for example, you have less violence, racism and a generally better standard of living and education.
Beyond that, you can improve the selection process through proportional representation. New Zealand and Germany are fairly good examples.
The US is stuck in this yoyo position partly because private interests have more influence on policy (through $$$) and partly because of the electoral college, which (like First Past the Post in a Parliamentary Democracy) gives arbitrary influence based on geography instead of people.
So you get this endless fight between two major parties that are constantly paid to represent outside interests and they won't change until the system changes to properly regulate private interests and it better (proportionally) represents the body of people who vote.
If the US had a better public education system, I think that you would see the changes I've mentioned above happen a lot sooner.
I think populism is just giving the appearance that the people (or the little guy) have more influence but it's a sham because populist leaders (including Trump) are still giving authority to the elite while they promise the opposite.