From my experience, the people who care more about customs are SFJs. Or, for that matter, xNFJs, or anyone with strong-ish Fe (b/c they're the ones hosting the events a lot of the time). I'd say that my NFJ friends care a lot more about tradition than any STJ I know of.
I think that in theory, yes, strong Fe can make it more likely for a person to value their cultural tradition and customs. In my experience too, the ISFJ and INFJ I know seem to identify themselves more closely to their culture than I do. There are maybe some conflicts within them about that but nevertheless they seem to feel it is part of them.
I think though that in reality this can't be boiled down to type and it's more complicated. For example, an ESTJ I know looks from the outside like he is very much into his own culture, and in a sense he is but in a more superficial way. Inside he has his own very particular world view and philosophy he constructed himself. I think whether or not you identify with your culture is more influenced by other circumstances, like exposure and experience of other cultures from a young age, etc.
In many circumstances customs are in direct opposition to rational mindedness.
- Special event and traditional gatherings
- Belief systems about life goals, values, purpose
- Approach to a problem situation
I'm reflecting some personal biases into this thread. I've scored as an ISTJ and INTJ depending on the test. I have a curious, floaty personality and mentally ask a lot of "what if" and "what about" questions. I have a strong need for efficiency and find it painful to do tasks that intuitively feel like an inefficient use of time (it's a real chore for me to make my bed or write long articles for my website, but I can spend hours of time planning a scenario to achieve the maximum result. I have a strong dislike of (in my mind) frivolous traditions like religious functions, weddings and other celebrations. I'm the least visible person in my extended family.
But I also value facts and empirical explanations for their credibility and put a lot of study into my field. I'm loyal to a cause I believe in. I use organizational tools extensively, though my home environment is very messy.
I don't see a clear division between ISTJ and INTJ. Using myself as an example, they seem one and the same.
I am really similar to many of those things you mentioned. Some family/cultural obligations that have to be done "just because" feel really oppressive to me. I think your culture is a part of your life so it's there and can be a valuable thing, but for me personally, some customs and ways of thinking are just old habits that make no sense and I just can't live like that.
I think the difference between ISTJ and INTJ, in a stereotypical sense, is that the INTJ enjoys exploring and discovering theoretical ways of making sense of things more than the ISTJ. I think an ISTJ would come to the point of wondering where the real, practical application and change can be made in the real world sooner than the INTJ.