Hillary's policy proposals all polled very high
Trump's policy proposals mostly polled very low
Who won the election?
Individual policy proposals DON'T win elections. They never have and never will.
This sounds about right. I think some elections can truly be referendums on a specific policy (or policies), but they are usually not like that. Especially midterms, which are almost always referendums on the incumbent president. Like it or love it, mdterm voters aren't going to be won or lost by who has the best policies. Those are, at best, what presidential elections are for.
As for some of what the article said - it wasn't as clear cut as "free college" = bad. A lot of the responses indicated resentment for free college from people who are struggling with student loans, and then you had a portion who resented college in general, and thought of it as elitist and not useful. None of this means the idea of "free college" is bad, but it must be
sold the right way with better messaging. Free public higher education is an admirable goal, and it shouldn't be held back by pure resentment. Reducing people's student loan burden would help ease that problem.
publicunofficial had the right take - at best, they were viewed as empty promises, because people don't trust that those promises will be delivered. Although, I argue that it isn't so much to do with Democratic leaders but politicians in general. You have to have some sympathy for people with that argument, especially ones that don't pay much attention to politics - look what has gotten done over the past 6 years. Nothing. Nothing worthy of note to the average joe.