They rely on donations, that part is correct. Are they in constant financial need so they are forced to ask users so often to donate? No, they are not.
Also keep in mind that while the server and developing costs of Wikipedia are one area of spending, Wikimedia spends money on a host of projects. Some of them you would probably consider more important than others.
Having no filtering certainly had its pros and cons, considering how much traumatizing shit google would throw at me as a child lol