It is too bad you have had this type of experience. However, you finished treatment with Invisalign treated by your specific dentist. As noted on this forum, your results will differ depending on the doctor you choose. There is no point in flaming the product, because Invisalign is a technique, not a product. To say that Invisalign doesn't work is like saying braces don't work... they are both simply ways of moving teeth.
Unfortunately, posterior intrusion happens because of biting on the aligners all day and night, unless proper planning is put into the movements to counteract this. If this occurs, there are other ways to make the back teeth occlude, but it takes a wealth of experience using Invisalign to move teeth. Most dentists and orthodontists do not have this extensive experience.
Moving forward, it is likely that an experienced Invisalign doctor can correct your issue without requiring grinding down your teeth or placing a mouthful of crowns to increase your posterior vertical dimension. You may find this thread helpful: Invisalign: technique rather than a product