I gotta wonder how yukkuri devolved from these stone-cold badasses to the hapless shitbags hopping around today.
It has a lot to do with the average personality of the members of a niche fandom of a niche fandom.
Most are male, socially awkward, obnoxiously intolerant and highly insecure so the results are expectedly powerful, cool (or edgy) characters/self inserts wailing on or screwing characters that should be more resistant to the attempts of your typical schmoe without any logical justification other than a stereotypical character flaw that cannot be overcome (being perpetually stupid just because of gender, species and other whathaveyous that appeal to or offend the average member of the fandom).
It is one of the reasons why some harem anime and manga have powerful and confident heroines quivering like sows in heat to the presence of the male MCs, because on average that is what the target audience want -_-