I think it's fair to say it's a leading theory. It certainly isn't uncontested; there are many scientists and philosophers who feel strongly about it in both directions. The unfolding argument claims it is not falsifiable and thus is not a scientific theory, but that hasn't brought IIT research to a halt. It's one of the most talked about theories of consciousness at the moment. So you may be right to say it isn't a scientific theory, but somehow it's still a leading theory! For some of the controversy surrounding IIT, see this open letter signed by 124 scientists (including three of the authors of the unfolding argument) https://psyarxiv.com/zsr78/