I disagree. Wikipedia is similar to Exercism on that count. A tiny fraction of expenses are hosting the encyclopedia. It's also necessary to pay people to program the software underlying MediaWiki.

People aren't bothering to edit anymore either. Search engine summaries, voice assistants, and now large-language models repackage information from Wikipedia in a way that discourages people from going to the website itself. Most low-hanging fruit is gone, and the standard of quality has increased.

There's a whole project dedicated to helping undergraduate students edit Wikipedia as a part of their coursework now. It's a great learning opportunity because a Wikipedia editor will check your sources more than the average TA. The flipside is that an undergraduate degree in the liberal arts isn't necessarily enough to write at a Wikipedia level, which is a problem.

These external factors are decimating the volunteer community and the visitor population. Spending on outreach, staffing, and grants to local affiliates is much costlier than having people wander onto Wikipedia and contribute, but that's no longer the era we live in.

I do know a lot about noncommercial broadcasting in the US though, and your comments appear superficial.

A sponsorship message is different from a call-to-action advertisement. The former is permitted, the latter is not. They are not different enough, in my opinion, but they are discernible.

Public TV and radio station finances are public information. Audience fundraisers are a meaningful portion of their operating budget (~25-50%), though it varies by market. As are program underwriting (up to 50% in strong markets), and often CPB funds contribute a few points (this is highly politicized and if you overindex on it, your news sources are likely polluted).