Hello. I’m not 100% sure if you’re saying that you have the micro/macro fetish and are asking how to better explain it, or if you’re asking /me/, or the general micro-people community, to explain how it’s different. But I will go ahead and respond under the assumption it’s the latter?
I totally get how it’d seem like a type of infantilism, and there are definitely a lot of ostensible similarities: wanting to be “protected” in some capacity (though a lot of people are into violent-ish giant/giantesses, but still being in someone’s sort of control and certainly protection of some sort), wanting to be literally/physically small, wanting to be largely dependent on someone else to “take care of” them. To address your description specifically, “small”–yes, “dependent”–to varying degrees, and “helpless”–no, not usually. (I’m sure I’m going to end up rambling for far too long and getting way too wordy, but bear with me.)
For a lot of people it’s not even specifically a sexual–or romantic–thing. Like, for me, it’s often equally about the sheer size thing in and of itself–more or less the excitement/thrill/adrenaline rush of being yourself in every way, but being like two inches tall and experiencing the world from that perspective, where everything is a big adventure, and everything is so intense and so much, just, /more/–like imagine how much more intense every experience would be. Like, whoa. I–and I think a lot of people–are equally interested in things like shrinking and then figuring out how to go about living on that scale like in the Borrowers or something as we are interested in the interacting-with-people/giants part–although this clearly refers to those who prefer to shrink over preferring their partner grow or already be immense, though I think in many of those cases entering into and having to survive in an established giant world is the same as being shrunken in this one. Some people do just prefer something along the lines of “one person miraculously becomes huge in the normal world” wherein the fetishist’s existence would be totally unaltered aside from the existence of and interaction with said giant person–in which case…
It’s also very different from wanting to simply revert to infancy in that, obviously, you’re mentally still as mature as you are now. It’s less about the physical interaction (excepting sexually, assuming that’s a part of whichever person’s particular agenda for it, as is almost but not always the case) than it is about the emotional/mental/intellectual. It’s largely about trust, and about the usually initial fear and eventual feelings of safety and trust that come along with interacting with and being handled by another person–and as such, it’s so much more about about “being /able/ to completely trust/rely on someone else” than it to “be completely dependent upon” them. In this regard, and on the sexual front–okay, basically all of it–is much more like an extreme form of BDSM, or at least the S & M part. And so going along with all of these things is a whole “being able to be vulnerable” thing.
And going along with that, to address your use of the word “helpless”–which I totally understand, and which seems like an obvious one to describe this–like, for me, I’m someone who is… fiercely autonomous? But that causes a lot of tension in most of my relationships, because I feel like I /have/ to be somehow removed from the other person and to keep them a certain distance from me in a lot of ways, which can also leave me feeling so much like I have to keep a lot of my difficult feelings and things to myself rather than share them with a partner, and feeling ultimately kind of isolated (I realize that’s definitely an issue to address, but ignoring that in this context). So in the context of the fetish, it’s much easier for me to not have to feel that way, both because a) I feel like I could act that fiercely autonomous way, but it will be less hurtful for both parties, because/and a) I will basically have to be as open and honest and trusting of the other person to survive.
Also, have you thought about exploring the enormous body of a hot person? Because wow.
Sincere “thank you” if you read this whole thing.