Nothing of this nature is instantaneous. Can you imaging wearing a device on your tooth that contains a battery, wires, electronics, that stimulates the growth of what is essentially a bone, for what will require the length of time a broken bone takes to heal, usually about six weeks? Assume they can cut that down by 33% and they can do it in four weeks. Do you get to EAT during the treatment, or does food in the cavity impede the healing, or is there a special cleaning required to remove food residue? Frankly, I would be very surprised if anything comes from this.
Preventing the carries in the first place is FAR better than filling the lesion in the tooth after the fact. In other words: "Look MA! No cavities!"
People wear braces. People have to have their jaw wired shut after surgery on the jaw bone. Both of those ideas were probably discounted as unrealistic when they were first proposed.
No one is saying this is a magic fix that will happen in the next few years, but just because you can’t see an immediate application for the process doesn’t mean that it won’t revolutionize how treatments of cavities are handled in the future. The fact that just a decade ago it was “settled science” that you could not recover lost enamel on a tooth means that we have already advanced our understanding of the human body.