When applying to a PhD program whose strength is not my concentration field, should I adjust my statement of purpose to match their area of strength?
It seems you are looking at this from the wrong angle.

You should not (primarily) tune your SOP to whatever increases your chances of acceptance, but to your interests. If you are "a big Macro guy", then what good does it do you to pretend like you are really into Game Theory? Do you want to do your PhD in Game Theory, even if you are not passionate about it (hint: you really shouldn't)?

Further, is it possible that you are actually not applying to the right school, if they have close to no faculty in your speciality? Why do you think this school is a good fit? If this question has a good (academic) answer, this is what you write in the SOP. If the answer is non-academic ("I like their sports team!"), I suggest you should reconsider applying to this school altogether. As you can see from browsing various questions on this site, being in the "wrong" grad school can be a terrible experience.