They may take a while to be completely killed off, but a fast & violent counter-assault can go a long way. You deal with a snake & cockroach infestation by killing every one you see, poisoning the ones you can’t, ignoring the fact the process will be messy, and then cleaning the place up & patching holes ASAP; fearing & negotiating with them doesn’t work.
I don’t disagree. And I am quite certain that ISIS is feeling real pain and taking real casualties for the first time in their existence as a... whatever it is. But they are an insurgency, and they are supported by the governments in Washington D.C., Riyadh, and Ankara at a minimum. They’re going to take a lot of killing.