1. Nobody complained about the efficiency of natural gas turbines. You can efficiently do a lot of useless stuff with deep negative externalities, and the fact it's efficient is not all that helpful.
2. Saying "the extreme far end would not be satisfied even by much better solutions" is not an excuse not to pursue better solutions!
3. There are many dimensions of this that people care about beyond the "global concern" level regarding "pollution and fuel consumption."
4. There are many problems that are significant and worth thinking about even if they are not the largest singular problems that could be included by some arbitrarily defined criteria