I know you've already mentioned that you strongly feel you are not an ENFP and only use Ne if you force yourself to, but to be quite honest, there are many flags that come up in your descriptions that read as "ENFP" to me. I want to keep this reply short, but a few of your comments that I personally resonate with 100%, are also some of the things other people have brought up as well, that may indicate ENFP as a possibility. (I'm just going to list them below with a brief take on it to make it visually easier to read)
-You feel like an introvert through and through
As already mentioned before, ENFPs are known to be the most introverted of the extroverts. This is because of the Ne/Fi combination. Ne isn't something you turn on or off, at least that's how I feel, since it's about making external connections and making sense of your environment. Unless you remained in some plain white walled room, how can one NOT make connections and see things in a larger framework all the time?? Secondly, using Fi as the aux function, ENFPs require that down time to pull away from it all and analyze their experiences to see how it all fits within their own framework of feelings and interests. Ne can be a very taxing exercise on the mind so when it's your primary mode of interacting with the world, you're going to need time to process things.
-You say you feel like some social chameleon
ENFPS are sometimes referred to being this way because we can read people fairly easily and wish to communicate with others in a way that is natural and fluid to them. To do so, we'll often shape how we react, respond, and carry ourselves in a conversation to adapt to how others are. I can't say that I do this intentionally, and feels more a subconscious attempt on my end. I've only been made aware of this fact by others when they say I tend to act differently depending on who I'm talking to. This isn't necessarily an Fe thing either from my perspective (though I suppose it could be), but just a means to better communicate with people, which ENFPs get a total thrill from
-You like the concept of people, but not necessarily invested in being that "people person"
From my experience, I often feel quite selfish if I'm perfectly honest. I do like people and communicating with them no doubt, but if I'm really honest with myself, I'd say it's more of a "tool" to expand on my knowledge of the world by gaining further perspective and incite into how others think and bringing that all in to add to my understanding. Basically, it's socializing with an Ne objective at hand. I'd assume ENFJs being Fe dominant, or perhaps INFJs are more people-oriented with that Fe for the relationship alone. ENFPs are people oriented, but I find I tend to just do my own thing, and people tend to come to me. (I realize this makes me sound like a complete ego-maniac, but I assure you I'm not) Also, if you are stressed or in a negative mood, you can retract and become much more introverted. It's happened to me before, and I felt like a 100% introvert at the time, but I only now realize it was because I wasn't my typical, positive self at the time, and pulled inwards.
-You have these seemingly deep seeded goals for humanity and desire for equality and fairness
This to me, seems strongly Fi, and as an aux function for ENFPs, we can pretty hard-headed and willful when it comes to protecting those internal morals and interests for right and wrong. Everyone wants to see other people succeed and do well in life, it's a natural compassion us humans all share, but wanting to take it to a point where it seems like you're ready to go on a crusade for such causes, and lead the change, sounds very ENFP or INFP for that matter, to me.
Oh, and another ENFP tendency, turning a "short" reply into some massive wall of text like I have just done since we tend to get super wrapped up in our interests and will focus all our attention on it
But just to be clear, this is all taken from my perspective as an ENFP. You may in fact be an INFJ, but those are some of the key areas, among others I found, that I wanted to bring up that raised those "ENFP" flags for me.