Your question sucks and your arguments are worse. "I don't like a thing, so why do other people like a thing." Not even worth answering properly.
A Shield Doesn't have an Edge, Right?!
Shield Hero and his rape allegations are a stand in for anyone who has ever felt falsely wronged. Had a GF say you cheated and made all your mutual friends hate you? Had someone accuse you of cheating on a test? Pretty much everyone has felt wronged in some way when someone else lied about something, especially given how naive and trusting he is to begin the story.
Things turn and he finds out the fantasy world he's in isn't so happy-go-lucky and it has slaves and a dumb church who hates him just because of the magic weapon he got. Oh would you look at that, we have a 'persecuted just because of who I am' theme.
Yeah, he digs his heels in like a dumb ass and becomes an edge lord because 'Fuck it, if they want me to be an ass hole, I'll be an ass hole', but the distinction for him from most stories is that he still does his fucking job, and the power fantasy swings in hard when, despite being such an edge lord, he still has devoted friends(yes slaves/pets I'll get to that in a second), he's still a thousand percent more competent at his job of saving the world than the other 'liked' heroes. It's a pretty clear, "Haha, chads suck, we incels actually know what we're doing" if you want to be cynical, but during the story, it's also pretty clearly shown that Shield's edge lord tendencies are fucking him over too, because even he isn't as good as he needs to be to win,
because he's refusing to work with the other heroes.
And at the end of the day, no matter what else you want to say about how 'edge-y' he is or deride that particular aesthetic in character development or story writing, he's still an objectively morally 'good' character. Given the choice to literally have his false accuser killed, he opts to (
sort of) forgive her and let her live. Yes, he does so in a dumb, spiteful, and morally fucked up fashion,(which appeals to the power trippers), but he still does an objectively good thing by not killing her for ruining his happy go lucky life. His 'I'm supposed to be liked' bullshit also starts to evaporate as the series goes on and he learns more about the world, and he genuinely starts to realize that the fantasy world people are racist ass holes and the shield heroes are always the moral compass, which is why 'a lot of' people hate them. So he digs in
more on the edge lord tropes in order to help all his half-animal people friends, because he's a good guy and fuck racists, I guess? Look it's definitely not how I would play the field, but give the guy a break, he's only an anime character.
Slaves and Pets as Waifus
Shield Hero needed a party. Stories about a lone edge-lord on his solo quest for redemption/revenge/self pity
very rarely have any staying power. So give him a pair of companions who literally are not allowed to leave his side.
Enter his slave and pet. Yes, it is wrong to keep slaves, but it can very easily be argued that Shield Hero rescued his slave from a far, far, far worse fate by buying and using her as a sword to his shield. He NEEDED someone to do DPS, and since no one normal would follow him anywhere after his rape allegations, he HAD to buy a slave. It's also shown early that he needs to use the slave mark to get her to actually fight for him to start, but to my knowledge(I only watched the anime so I'm not exactly a perfect expert here), he only really uses it later on to break her indecision/fear or enforce his will as the Main Character when she's trying to be all selfless and loving and protect him or some dumb anime crap.
I want to say again, slavery is bad. Owning a sentient 'pet' is bad. But Shield Hero is ultimately very protective of his waifus, and they all grow to become a genuine family before too long. Sure, it's a little fucked up that he doesn't remove the slave mark (again, I don't remember if he does so eventually), but remember, HE DOESN'T HAVE SEX WITH THESE YOUNG GIRLS. (Again, to my understanding) Regardless of the fact that he is using them as child soldiers, he's doing so out of naked necessity and it's an objectively better fate for both of them than if they were with literally anyone else in the fantasy realm. Yes, relative morality exists, and yes, Shield hero is the good guy in a world that repeatedly tells him to go shove a pine-cone down his urethra.
In summary&TLDR
There's lots of reasons to like and dislike Shield Hero. Power Fantasy, Sticking it to the Chads, lovable Waifus(even if they are paper thin), edge-lord battle transformations, and neat video game rules in a fantasy world, among many others. You probably just wanted to make people angry with a dumb question, but I genuinely hope this was at least a little enlightening about why
anyone ever that isn't you could like Shield hero.