Not saying font designers shouldn't get paid, but they mostly aren't making things "completely by themselves", they are mostly making derivative works from things that exist, without any consideration for the original authors.
Everything is derivative, there is nothing new under the sun, and your argument proves nothing.
Sure, but with fonts you have basically one level between the font they are 'developing' and the one they are copying from. There is work involved, but very little of it is creative work.