I was unaware the bnha cuck memes were a factor in the decision to write btz, but I don't feel like it's a very fair comparison.
Romance is NOT a major factor in BNHA. Like at all. Granted I'm only on season 5, but despite the fandoms fixation in shipping I think Midoriya, Mineta and Denki are the only male 1A students I recall who even show any interest in romanc. You could headcanon most of the cast as aroace without ever contradicting canon.
Midoriya's primary motivation has ALWAYS been to become a hero. His interest in Ochako is secondary AT BEST, and based on what I've seen this far its such a big part of his character that the author could have ended up with one of the other girls without it seeming like it came out of no where (We know he was attracted to Mei at least.)
So fans acting like "Losing the girl is the worst thing that can happen to a guy." really is not consistent with Midoriya's character.
The fact is, if Midoriya was forced to choose between being a hero while staying single forever or marrying Ochako but never getting to be the hero, he would obviously choose the former.
In contrast, this is very much NOT the case in regards to Re:Zero. Romance is a huge part of Re:Zero's focus. Both Subaru loving Emilia, Rem's love for Subaru, Beatrice wanting that special person. Hell, basically all the Sin archbishops save for the gluttonies seem to have having a horrifically twisted view of love and relationships as their primary character flaw.
This goes especially for Subaru. Emilia a HUGE part of his motivation, and I would say prior to losing Ren at the end of arc 3 it was almost his ENTIRE motivation.
So the readers being upset about Subaru not getting the girl makes considerable more sense when compared to readers being upset at the idea of Midoriya not ending up with someone.
I think maybe if Subaru at least got some other girl like Rem or one of the other royal candidates, or even Fredrica or someone might make people feel slightly better about the situation, but thus far you've only confirmed that Emilia will end up with Julius, which I think is why a lot of readers are more focused on the "cucking"
Also keep in mind, not every fan of the series og are necessarily super invested in Julius as a character. Personally, aside from Aldebaran, I find the other knights to be among the least interesting characters in the series. I mostly watch for the members of Emilia's camp, the royal candidates themselves, and the Witch Cultists.
So even though I am really enjoying Dogshow, and will hopefully have time to read No refunds once it's finished, I can't say I am very likely to get invested in Back to Zero.
…Okay, backstory on the BNHA thing: for like two weeks after the manga ended, I ended up getting swamped with so many fucking cuck jokes out of absolutely nowhere despite not even having watched any of it since Season 3 was airing. But then in the midst of this I realized “Wait a minute. Unrequited love would actually totally fit in with the themes of BTZ, and it has this number of other benefits, too.” and thus decided to try it out. Did my annoyance introduce the idea? Yes. But it was not why I decided to go ahead with it.
Also Subaru IS actually confirmed to end up with someone and I’ve posted about it a fair few times. I’ve even considered changing who it is going off of other people’s ideas, but so far it’s held firm. Though frankly, the idea that someone HAS to be in a romantic relationship in order to be happy — and furthermore, the idea that women are prizes that need to be obtained by men in order for men to be happy — I really do not like that philosophy.