Yes what you are saying is true and it is our right and duty to protest that decision. When will they sanction something you do like and need like Signal or cryptography? Are they aware of all the bad that comes about via http? Or cash?
Well, the big legal limitation for these sanctions is that they apply only 'across borders' as OFAC can only sanction foreign entities (e.g. in this case asserting that TornadoCash-as-organization/project is controlled by North Korea), prohibiting U.S. citizens and companies from dealing with or assisting that foreign entity.
There are a variety of sanctions mechanisms. Tornado didn’t have to be controlled by North Korea (it isn’t), just used by them to fall afoul of U.S. law.