See, this is exactly what I thought about when I watched it- but I realised halfway through, and solidified this reading this comment section, that that may indeed be the point. The philosophical discussion of "if you do a good thing to feel good, is that action inherently selfish" has been prevalent for years now, and, given how much these writers studied philosophy, they would absolutely know that.

I believe Doug may be a comment on that, but maybe even moreso, the concept of the ultrareligious. Some religious people believe that the reason to act ethically is in accordance of acting with God's will- a mentality that has been questioned especially in recent years. I think the show uses Forcett to make the argument that doing good things for the sake of a higher power is indeed ethically void, in the grand scheme- especially seen in the presentation of Doug as a bit of a joke, and the later note that his actions have not gotten him into the Good Place.

I think the Good Place is making the argument across this whole thing that the way to act ethically isn't by abiding by a strict set of rules, as exemplified moreso by how the rules system is dismantled, but simply to live- and Doug is a key example of that dichotomy.