I found this interesting and a little underwhelming in terms of depth but it passed and MIT is a highly ranked institution. Such variations perhaps depend on your supervisor. https://dspace.mit.edu/handle/1721.1/144828 *I do not in any way judge the merit of the work as I lack the time expertise and obviously a committee from MIT did and found it worthy.
To be fair the next one I pulled up was also 128 pages and a similarly small bibliography. https://dspace.mit.edu/handle/1721.1/130209
I read the abstract and scrolled through it. I've never seen a dissertation like that. But I can't comment on the rigor for the following reasons: It's not my area of expertise The writing style is not APA I couldn’t determine what type of study it was (i.e., methodology) There doesn't seem to be any data collection (primary or secondary) I don't understand any of it, TBH. The first-person writing (although okay in APA) seems a bit much.
To be honest, I don't think there's much you can do with philosophy research. Once you start testing people's behaviors or thought processes, you're getting into social science and cognitive science. It could be appropriate to just logically argue your position.