Pretty much, if you want to do literary criticism and publish articles in that field, you can. You don't need a license; everyone is "self-appointed." People who don't want to - make excuses about why they can't. Time? Money? People who have non-academic jobs often pursue expensive and time-consuming hobbies, so it seems strange to say that an academic who is supposed to be doing 40% research does not have time to do much of any. The lifestyle of the professor at an R1 is pretty easy if you don't do research. You can make it hard for yourself, by undertaking many other non-research projects that are immensely time-consuming.
The biggest hurdle might be not having access to a good academic library.