I doubt that folks with a solid diet, high in sulfur would find much benefit from NAC.
However, as someone who's gotten to use it first hand and have dealt with lifelong, mild inflammation (puffy fingers, clogged nose here and there), it's definitely been a huge quality of life enhancer.
NAC interacts with a lot of things. Not just glutathione.
It modulates glutamate activity in the brain. That’s a key neurotransmitter. It’s why it can be helpful in some specific psychiatric conditions, but also why many people discovering it to be cognitively dulling or to induce blunt effect.
It also interacts with trace minerals in your body. Taking it for a long time can reduce these levels, creating multiple secondary problems.
The list of things it does goes on and on. It’s not a simple supplement for glutathione.
It also doesn’t quite live up to a lot of the incredible sounding papers for many conditions. It’s really common to find papers or even small trials purporting to find amazing effects from supplements that fail to replicate at scale. NAC does have some legitimate applications and is even used medically for certain conditions. I’m a little more skeptical that all of the amazing positives for every condition under the sun will hold up.