You were making an argument that some people's fixation on dick size is, in and of itself, evidence that dick size matters. Applying that logic to other parts that also have a tendency to be fixated upon was a fair exploration of the argument, not a derail.
You basically say that although breasts do get fixated upon, they only matter in so far as some people have a personal preference for it or may treat you differently because of it, but it doesn't really have a big relevance on actual sexual satisfaction. And if you say that, then why would it necessarily be any different for dick size?
Probably because you don't stick your tits inside a man nor do you generally cover a body part of his. You can do titty fucking but that is more niche and isn't really standard.
Given the fact that is quite common to have PIV sex it is quite obvious that size is going to play a factor. To say size doesn't matter or size plays no role would be to ignore the fact that physical incompatibilities exist. You can be too small or too big. A combination of too long or thick. Even things such as being a particular shape but given your size that shape becomes somewhat problematic when at a larger or smaller size it would not have been. It may limit what kinds of sex someone can have which can definitely impact their overall experience and satisfaction. If you are too big then you might not be able to go as rough or if she really likes bodies slapping, it just may not be an option. Or if you are too girthy in combination with your link you may not be able to slide past her cervix which means if you go deep BAM, insta pain for your lady friend. Quickies as well may not be a thing or you cannot target a specific area. Maybe you make her sore too quickly. On the other hand you may be too small to provide a full or deep sensation. You may very simply not be able to reach one of her pleasure spots such as the posterior fornix. Maybe she has a big butt and her hips are tilted just so that it can block you from entering period. She may not even feel you as the stimulation threshold was not met given that people have varying sensitivities. On the flipside you may be able to have nothing but pleasurable sex as there is no chance to bash your partner's cervix, rub her raw, or any pain other than perhaps slipping out and fking up your entrance which would be universal to all. Quickies would be a thing as it would require less warm up to accommodate a smaller penis.
The size of her vagina also plays a role buuuuuut given that the vagina is an internal organ, this is often overlooked as we are visual creatures and will turn our attention to what we can see. So her size while relevant is irrelevant :\ This would explain why there are a lot more men who are so deeply concerned with their size.
Size shaming though for women revolves more around slut shaming which is a whole different can of worms.
There are workarounds for some of these problems. However it should be noted that while there may be workarounds, not everyone cares. So the degree on which this matter will vary from one to another. Also some matchups may have no workarounds as far as PIV goes.
A lot of us are average and when paired up with average seems to work quite well. Not too many problems. That said, that doesn't indicate whether or not they are having what they might consider the ideal experience. That is left up to the individual. It should also be noted that the penis while not only a mechanical object can play a big role in appearance. Some people will have visual preferences for the look and the size.
Now you look at this and you'll notice that they both have cons and benefits. One would think they would be on even ground, nah. To use wally as an example. People similar to him are not very uncommon, (maybe not to the point he takes it) however the reverse of wally where it is someone soooo insecure about the mere fact they are above average or big I have yet to run into. Maybe huge but even then i have yet to run into. I come across a lot of pride, being content, and glad I'm as big as i am because I could of been smaller attitudes.
We could look at something unrelated but similar. If we look at race we can see it doesn't really matter in theory. It may come down to be personal preference for appearance........but yet it is an issue, an absolutely massive issue in different places. That is what I want to focus on. Why is something that otherwise shouldn't be an issue is blown up to be a much larger one that it is. Clearly there is an issue. So if we run back to dicks we kind of see the same thing. They aren't really that important in the grand schemes yet their importance is blown up. Women's appearances aren't really that important either yet it is blown up. So what happens at the end of the day is that yes they actually do matter. In a perfect world it wouldn't....but this isn't a perfect world.
So why are smaller ones routinely shat upon? why is being small viewed as such a negative thing. Why is it a go to insult or to add insult to injury?
Why is being large something one might be considered to be "lucky". Why would one appreciate the size they are because they could of been smaller?
Why are things not the reverse? Heck why not equal? like I said before if something truly didn't matter, we really wouldn't focus so much on it. I'm sure many men have been mocked for having one less fold in their eye lid,their ankles are more flat than pointy(visa versa), or the thickness of their shin is a little less than the average shin...oh wait no, no they haven't because no one really cares,....it doesn't matter :\ hell I'd go so far to say as most men haven't even considered that crap because it doesn't matter.
Clearly there is a problem which is the point I'm driving it. We are social creature and what others think of us and how others treat us does affect us all at some level.