[Author here] A more careful wording of "will it work if everyone does it" would be "if many people do it, does that reduce its feasibility for everyone else"?
This addresses the arctic circle and hunter-gatherer examples. Obviously there are no one-size-fits-all solutions in life. Solar panels won't work above the arctic circle, EVs won't work in an area with no roads, hydropower won't work in a desert. But if I install a solar panel, that doesn't interfere with your ability to also install a solar panel.
"Not enough minerals, not enough land, not enough batteries" would be a real problem if true, but my understanding is that it is not true. Of course we have a lot of work to do in developing mineral sources, scaling up battery production, and so forth. But I have not seen a credible source indicating that it cannot be done. Do you have any such pointers? (The actual trends so far have been very strongly in the opposite direction: the more batteries we produce, the cheaper they get.)
As for this:
> He has rightly shown that offsets cannot work for full decarbonization, but so what. No one thing will.
The limitations of offsets are different than the limitations of, say, solar power. It's absolutely true that solar power can only be part of the solution, but when you put solar power together with wind and storage and (pick your favorites) geothermal, nuclear, etc., you can get to a complete solution for power generation. In this picture, solar is providing an important contribution.
Offsets, conversely, cannot be composed with other tools to achieve a complete solution. If a cement plant operator pays to preserve a forest, who is going to address the (ongoing!) emissions from the cement plant? Not the cement plant operator; they already did their part, they purchased an offset.