We can see it through many recent events.
In UK, most people voted based on emotions, not rational thinking.
They was cheated that leaving EU will means more money for their health care and no more immigrants.
Now, when they are finally aware what they did, they already collected 2 millions votes for new referendum.
Only politicians are qualified to make such hard decisions, because they know all facts and in direct negotiation can always make some good political deal or compromise.
They are, after all, direct legal representatives of their voters.
I do not think that direct elections are a good idea, just by the fact that the pure exercise of democracy does not work.
The idea that a simple majority decision of the people (+ 50%) is a democratic exercise has been overtaken by the current dimension of the concept of democracy, in which all need to feel represented.
If the exercise of democracy was simply the decision-making of the majority, most present in a room could decide that it is okay to beat up one of those present.
Well they could. But recognizing that could happen to anyone constitutions were set up. Sets of basic rights and rules that inform a lot of decisions. And are harder to change. Direct democracy could have the same framework. See the case of countries that rely more on referendums like switzerland for example. Not perfect. But what better options are there than democracy?