If you agree that driving to shul is wrong but aren’t judging the person. That is fine. But if someone states that she/he “accepts” that someone chooses to break halacha and accepts any way someone chooses to serve H-m, that is wrong. there is only one way to serve H-m and that is by following the Torah (which really means a bunch of ways of serving Him but all those ways have to be Torah True.)
When you say, You dont know if that person driving to shul brings them closer to follow Torah Judaism. It doesn’t matter. You can’t do something against the Torah in order to do other Mitzvos. I still don’t say that you should judge these people. Maybe they deserve a much larger Gan Eden than someone who is supposedly very frum. who knows! But NOT because they drive on shabbos. It is despite it.