It's interesting that the author mentions this, but doesn't make a connection between feeling burned out and feeling that they have to be personally responsible for everything the company does.
I don't even disagree with many of the demands of internal "activist", but the strategies they use (walkouts, trying to keep everyone outraged as much as possible) seem ineffectual to me: The main effect seems to be that it makes ordinary employees feel more burned out since they're made aware of many things that they're suppose to be angry about but at the same time they're powerless to change them. That's a recipe for burnout.
I get that the thinking is that ordinary employees are not powerless due to collective action, but for that to work you have to be a lot better at picking your battles. You can affect one to two larger things per year, so getting up in arms over every (comparatively) little thing just has the effect that your activism achieves nothing but burn out the people who want to have on your side.