Depends on the action. Gluing oneself to the street in order to prevent 5% of 2% of an industry that is rapidly shifting to EVs is questionable, for example.
Heard about someone who glued themselves to rails before a coal plant. Allegedly that prevented the equivalent of 800 years of average western european lifestyle emissions. Here I'm trying to get my own climate warming impact to be at least close to zero (and failing), and this dude has a 10x impact by doing nothing but sitting on rail for a bit. The cost is losing 9 months of their life on jail time. (Definitely an interesting proposition were it not for (1) the likely reality that some other coal/gas plant just spun harder during that time, and (2) that I'd likely get more jail time because I did it knowingly and found it worth it and as such it's not a sufficient deterrent.)
I'm trying to rehab a 10th of an acre of prairie that used to be temperate rainforest.
That won't even offset my own impact on the rest of the world. But I'm showing up to meetings with other people, giving advice, hopefully some inspiration, as well as plants to make the process a little more accessible to other people.
Best case at the end of this, I've helped dozens of people reduce their carbon footprint, and they've helped hundreds do the same, and so on. All of us will still have a positive carbon footprint, but we've called into question what the average footprint should look like. Us and a hundred other people who think about things like transportation or building standards or entertainment.
The end goal is that becoming a giver instead of a taker represents sacrificing 10% of your lifestyle instead of 75%. It's very hard to peer pressure people into giving up 75% of what makes life worth living.
Is the idea that downstream consumers had an easier time retooling their processes to an entirely different power source than buying from a different coal plant? Questionable, at best.