Some random thoughts:
The “path to impact” of content creation is vague/diffuse. Compare with something like GiveWell top charities, which are claimed to be “proven and effective”. Then also compare with something like existential risks reduction, which is uncertain but claims to be neglected and have a huge amount of impact.
How does content creation fit into this framework? There are various neglected parts of content that can be improved. The impact on a single person is most of the time not that great, so inasmuch as there is large impact to be claimed, it must come from a lot of people consuming the content. We don’t really have a great idea of what people are hoping to find (there’s some work on this, e.g. “Why We Read Wikipedia”), so how do we know we’ve helped them?
The type of impact that content has is of unclear value. A lot of content that gets the most pageviews serve as entertainment. Others satisfy curiosity, helps with a school assignment, helps people form more accurate beliefs of the world, etc. These are all quite different from “saving a life”, so it’s unclear how to weigh this against typical charities.
Potential paternalism? Charity can “correct the market” by giving money to people who are unable to spend (the poor, animals, future persons). But content creation has less of this problem: If people find the material useful, won’t they fund it or pay for it?