I don't disagree with you at all. As I said, it's a great tutorial for the fundamentals and the securtiy considerations are of course important still but I think it is also true that there are more recent approaches to writing web-apps and I would recommend exploring those.
I'm a bit surprises about the - in my view - slightly excessive downvoting and I think it would be good if those who did downvote could explain why? Not because I'm too fuzzed about XP but because I would really like to know if others really disagree with the notion that a pure CGI script as back-end for a web-app is a bit dated, in particular if the web-app basically handles a database with forms for viewing and updating records.
I mentioned database interfaces because the OP described a scenario where a CSV file would basically be used as a database - including update operations. To my mind, this is going to be highly problematic in the long run and I'm not sure if your post agrees or disagrees with that position(?)