On the flip side, Ørberg is a textbook for children, perhaps teenagers at the latest, and like most such textbooks it is in no hurry, so you’ll need to stick with it for quite some time to get results. That by no means makes it bad or unsuitable to whoever is reading this comment, but I can imagine how it wouldn’t work well in a typical introductory college course, where the instructor’s aim is to cram into the students’ heads as much Latin as possible in the semester or two they are given.

If done well, the grammar-centered approach leaves a lot of blanks, but the blanks are more or less “just add vocabulary”. So assuming you’ve retained whan you were taught (!), once you want to read any classical text, you can take a dictionary and work through it. Do that enough times over a few years and eventually you’ll be able to get rid of the dictionary. Again, you see why one would choose to do this when one needs to equip their students for any text to the greatest possible extent in a limited time; but that’s a different goal from having them read some texts as soon as possible. And it’s not always done well either, of course.