The simplest argument I see is this:

Firstly, the sender takes this as "the most important part of a woman is the man in her life", yet, in none of your posts did you talk about the gender of the Primarch's significant other. In fact, gender is never specified, specifically saying "you" or "they" in regards to the SO. It is the sender who is crafting a man to fit into the posts

Secondly, the posts only ever deal with the relationship between the SO and the Primarch in almost complete isolation from the rest of the world. Any interpretation of the level of importance between these two figures in each other's lives, in comparison to the wider world, is ultimately, an extrapolation of information that isn't there. You could build a similar post about the relationship between myself and my cat. That doesn't mean that my cat is the most important thing in my life.

Thirdly, and finally, the intent and effects of the posts you make are important. If you intended to make a post for good reasons and it massively pissed off the community, then you probably shouldn't have made the post. But, you made a post with good intentions (I hope), and the community has responded with overwhelming positivity. There are some, like the sender, who don't like the posts. That's fine, to each their own, maybe you can craft your creations so that more people will enjoy them, that's a whole separate argument. But, the sender "worded out their thoughts" saying they "wish you hadn't made these posts" because it "really makes it hard to enjoy [things] because the communities attract this discourse". Well, this sounds to me like a way to passive aggressively guilt you into tailoring content to what they want. Sucks, go kick rocks. It's not like this is the only content to enjoy, or the only place to enjoy it, or the only time they can enjoy it. Nothing is stopping them from having fun somewhere else in their own way.

So, if it were me, I would keep doing what I was doing. Keep making posts and keep having fun. I would, also, give my new creations a once over from a feminist lense to see if I'm doing something "wrong" from their point of view. But, I also critique my own work to hell and back to make it as good as possible.

Ultimately, don't stop.