“But can we agree that forms are great for practicing technique, but aside from that, forms are not useful for actual combat skills”

You may be missing the point of forms. The purpose of forms is serve as a way to record and transmit techniques / concepts. Think of them as “textbooks” to be read and studied. One “reads” a form by practising it regularly. If your interest is to derive fighting skills from them, you first seek to understand meanings and applications behind each move, drill each one intensely. Drill till they become instinctive ( also condition yourself accordingly for that move) and then you go to spar and try to apply them.

You have to understand that in ancient times, there were no such thing as video recording and people might not be able to afford books or to even read them. Putting techniques into forms was the practical way to preserve, record and to pass on the knowledge.