I wholly agree with your perspective. My suspicion is that that is an outgrowth of an abuse of statistics, broadly speaking.
For good or ill, too many voters behave predictably: too many voters are pretty much set in their ways and their loyalty to one party/candidate or the other is often assured. Since politicians think that, on the account of these “average” voters, all voters behave predictably, they are given to parroting robo-liners without seriously trying to reassure voters who might or might not vote for them, on the basis of what they might say and do. But 10 or 20 per cent of voters, especially when they do not fit neatly into political formulas, are a huge deal — they are responsible for turning the election one way or another, which they did, of course, in 2016.