This is absurd and shows some ridiculous entitlement.

Software development is not just a drive-thru restaurant where people just make an order with their preferred menu, and 30 seconds later it is handed it out to you. Developers have to balance a bunch of priorities, deal with bugs, make sure that new features being added can be maintained in the future adequately. It's also not easy for anyone to just drop by and submit a huge piece of functionality without making sure things works as expected. And they are doing this all while getting basically no money in donations (~3000€/month, for 3 developers is less than minimum wage for pretty much all of Northern Europe).

If you think it's just a matter of "they don't care", go ahead and write the code yourself.