As easy as it is to blame the American people for this, that’s not quite the case. The “tax scam bill” is deeply unpopular (hovering at about 25-30% approval) among the general population. It’s the Republican Party who has thrown all of its muscle behind committing to it.
Under normal circumstances, tying their names to a bill like this would be rejected out of hand for being political suicide, but these are far from normal circumstances. If there is anything you can blame the American people for, it’s that.
It also doesn’t solve nearly as many problems as you’d think. Currently, Justin Trudeau is actually the oldest of our three major party leaders (Andrew Scheer and Jagmeet Singh are both still in their 30s, IIRC).
The problem is that it’s a tax cut that disproportionately benefits the wealthy (among other things, like cutting down the ACA and giving tax exemptions to one particular private school) at a time when income inequality is popularly seen as a major societal crisis and resentment towards the wealthy seems both very widespread and extremely well-justified. Add to that the fact that this bill so obviously doesn’t have a popular mandate, and it becomes very easy to see it as written by the wealthy, for the wealthy, without a hint of popular legitimacy.