One of the problems with the Spanish course is that all the later content (past checkpoint 5 or so) just stops explaining things at all, so it's up to the user

One of the problems with the Spanish course is that all the later content (past checkpoint 5 or so) just stops explaining things at all, so it's up to the user to figure out things like how the negative imperative uses the subjunctive case. It's okay if you've taken a more structured language course in the past but I can imagine people starting from scratch just getting completely lost at that point.