It's not an excuse. It's just reality. Presidential elections, at least since suffrage, have always been won more on a candidate's personality and likability than on issues. We do have to be strategic in selecting our nominees so that they pass that test. Romney never did and it was understood and stated by many observers during the primary.
Absolutely, the ignorant electorate is a problem and they deserve blame for that. But that's a problem we should all be well aware of and strategize around if we want to win. So we deserve blame for not doing that.
Also, this is not so much about Romney being rich, but about his out-of-touch personality and him not having a compelling life story for how he made his riches that people could relate to. Trump might have had other problems as a candidate, but he is a rich guy that people could relate to on the drinking buddy level. Romney is just the Republican version of John Kerry.
That is true of independents, but Romney's problem was not with independents. It was with Republicans. That tells me that your supposition is intrinsically wrong with regard to Romney.