[MENTION=6561]OrangeAppled[/MENTION]
Interesting opinion. When I get home I will check up on the ISFJ personality more closely, but for now I've something else to say:
Although you suggested me to let go of the Fe-Fi stereotypes, I feel more prone to Fi-Te than Fe-Ti.
Assuming I've Fe, it means that I've Ti. But Ti style of thinking doesn't sound like me, nor does the Fe style of feeling sound like me.
An ISFJ is different from an ESFJ however, but they still have the 4 same cognitive functions, just in slightly different order.
Although my typing isn't the best, I'm inclined to believe my mother is an ESFJ for various reasons, one would be her generousity that always clash with my beliefs. It kind of feels like I'm the stingy, self-absorbed person who wants to be given, whereas she's the generous, selfless person who wants to give and can't understand why people wouldn't appreaciate her concerns. And since ISFJ and ESFJ both share the same functional stack just in slightly different order, yet I feel like the complete opposite of her, it makes me highly doubt being an ISFJ.
Therefore I've doubted both Ti and Fe possiblities.
This is an often used method of understanding type, and IMO, it is totally wrong. No types "have" the same functions. Your dominant function is your ego and the other functions exist in relation to it - these are mental attitudes in your psychology. In reality, we all use many forms of thought processes that do not all neatly fall under 8 categories. Your type is the prevalent attitude in your psychology that affects your visible personality.
An ISFJ wouldn't relate heavily to Ti style thinking... But I'd see a lot of INFPs who do, because it's Introverted Judging, and they are grouped by Jung for a reason. They have a similar attitude, even if they prefer a different way of reasoning. If you relate to ISTJs but feel you prefer Feeling (value motivated) over Thinking (impersonal classification), then ISFJ makes the most sense. "Value systems" are not the sole domain of INFPs or even Feeling types, and honestly, IxFPs rarely experience it as a "system" (although I may use that term in the context of typology discussions, I would never describe myself as having a "value system"; to me, that phrase sounds like Je mentality).
MBTI is a "best fit" system, as no description will fully and accurately capture you as an individual. The key is to look past details (which serve to illustrate) and see an overall, basic mentality each type is trying to capture.
Everyone keeps noting how "Si heavy" you come across, and yet, an INFP's ego has Si pretty far down the totem pole, so to speak. Why not consider being a Si-dominant type? IMO, finding your dominant and then considering the auxiliary is a far more accurate way of typing, because looking at whole function stacks is misleading as to how type works and how functions will appear/be experienced in relation to one's ego.
Don't look at whole ISFJ profiles, which have a strong bias towards American Women in them (male ISFJs may not have the "hostess, caretaker" flavor of Fe they often give in ISFJ profiles. Try reading Jung's & Van Der Hoop's descriptions of the Introverted Sensing Type and other profiles which talk about Si-doms. Lenore Thompson's book is pretty good to use in this way, as she discusses type by the dominant function, and then breaks them down further by auxiliary.
Also consider if you are a dominant Pi (introverted perceiving) or Ji (introverted rational aka "judging") type. The mentalities of these are very different. Pi types use Je and Ji types use Pe, and so all IxxJs and all IxxPs, regardless of function, respectively share an "attitude". This is because their mentality is structured similarly even if they use different functions. Without grasping this, people come to many erroneous conclusions about type, as they tend to oversimplify "use of functions" & use that as indicators of type.
IMO, if you relate more to an ISTJ than ISFP, then you're probably an ISFJ, not INFP. It doesn't matter if ISTJs and INFPs "have the same functions" - because really, they have very different "roles" in relation to their ego, and this results in a very different mentality. The ISTJ has an "Pi+Je" mentality. Whereas INFPs and ISFPs share the same function preference for the ego, and they both have a Ji+Pe
mentality, even if their perceiving preferences are not exactly the same.
EDIT: Carer to explain further why you've ruled out ISTJ...?