I respectfully disagree with the dead end part of your argument. A dead end would be if they provided no value.

While the environmental and social downsides are massive negatives on the tech, it is actually doing something.

Past iterations are completely useless, but more recent iterations show us a more polished side to LLMs that actually do enhance how we do some things.

Is it worth it? My gut says no, but its both too late and too early to call it. (late in the environmental and societal impact, too early in the tech iteration)

As far as the "dead end" argument goes, I have to say that's a hard disagree. Humanity is filled with technological advances that "stand on the shoulders of giants" and improve on previous techs. Even if LLMs themselves don't prove to be the thing that we've been promised by the people driving it, it is taking us one step closer to AGI (whether that's a good goal or not, that's still up for debate)

From here on, I think there's still quite a bit these models can improve, and I hope a lot of that improvement goes into making it more energy efficient, more water efficient in turn.

If by a dead end you mean that we can't reach an AGI from an LLM, I think that's correct, however an LLM might help us figure out what is needed for an AGI.