Some men will always be unappealing to all women in a romantic sense.
I personally think there are some men out there in which no woman ever will them appealing enough to have a romantic interest with them. I don’t believe in the idea of there’s someone out there for everyone. I think for some men, there was never that someone for them. Like these men could have everything in order with their life along with continued self improvement. Yet none of it will matter as far as having a woman be attracted to them. It’ll just never happen for them. The reasons as to why they are always unappealing will vary. Ranging from just being too different for everybody, severe level of being neurodivergent, etc.
Now I also think that this number of these men is relatively small. I also think most of the men who think they fit into this category actually don’t. Most of these men could find someone if they worked on whatever needs to be worked on (social skills, personal wellbeing, etc). So the 80/20 thing is moot because men of all shapes, sizes, ethnicity, etc have experienced having a SO in their life. But there will always those men who will simply never have a woman be romantically interested in them.