They havent said dont donate, they have said donate to client maintainers instead.
As they point out in the post, Jellyfins No1 problem is keeping their clients up to date with new features and design polish.
They have identified that the money being donated to them would be much better donated to the maintainers of the clients to encourage them to do more/better work, but they dont feel its right that they choose how that is distributed and they want the users to donate to the client they favour most. I think this is great, and hopefully some of the clients which have been dragging recently can get some donations and encourage some fresh development on them.
Three years is nothing, and money isn't always reliable coming in.
Nor does it factor in some unexpected expenses.