You wouldn’t literally tax people based in advice they gave; instead it’s a matter of using different funding mechanisms that are incident disproportionately on different groups. Funding stuff with debt is a de facto tax on future generations. Instead, you can e.g. tax 401k withdrawals above a certain amount, higher property taxes, taxes on pension withdrawals, etc.

You can say that not everyone who draws on a 401k contributed to the problem, but that’s besides the point. If you forgive the debt, then nobody who is going to bear the cost will have had anything to do with creating the bubble.