That literally makes no sense. You'd rather a rectangle telling you to consume sugar than a rectangle asking if you can support an organisation that provides a service you use?

Ads are easier to block, or just ignore as a fact of life. Donation requests might cause irritating cognitive dissonance.

then you should be asking for a paid membership

The point is, of course, that you don’t really want to pay for it but feel sort of guilty if reminded that keeping it running costs money. Textbook example of cognitive dissonance.

That sounds like the donation request is being effective...