It sometimes happens that I receive referee requests for theoretical papers which deals with the same phenomena I do in my research, but from a totally different specific theoretical starting point. I am familiar enough with the "competitors'" theoretical framework that I can read the papers, but they more often than not, it seems that the papers I receive are limited to only basic results of the kind I would not publish myself, but rather leave for my memoirs or a lecture note.
I realize that I am of course a bit biased, since I actively dislike that theoretical framework. For that reason I also have a hard time judging if the papers actually make some kind of incremental contribution, which would warrant publication.
For these reasons, I mostly decline reviewing such papers. But recently I have started to doubt whether I am, in this way, a bit too soft. If everyone, who are not active researchers in that very specific theoretical framework, decline to review their papers, we just end up with a lot of sub-par research being published. On the other hand, I don't want to become one of those petty referees, who will only accept papers that does the kind of theory that I find best.
Are there any good solutions to this dilemma?