Kudos to you for successfully delivering in a similar situation. That said, I think your advice is a bit cavalier. The industry is littered with the carcasses of failed rewrites. The fact that you have done it in one context does not mean that this team can pull it off in another.

I'll also say there's a lot of semantics at play here. What is a "rewrite", what is a "test" vs a "document", what is "functional"? I read your main point being that one should avoid sunk-cost fallacy and find the right places to cut bait and write off unsalvageable pieces. The art of major tech debt cleanup is how big of pieces can you bite off without overwhelming the team or breaking the product.