He's a screen villain. The better villains--whether completely fictional or based on a real person--by their very nature are irredeemable and not attractive in any sense (e.g. Sidious, Casino's "Nicky Santoro", et al.).
I meant more cinematically attractive. He's not enjoyable to watch, and I have difficulty believing anyone would work with him, willingly or unwillingly, which makes the whole idea of him being a kingpin, never mind a CEO who'd still have the potential to be a beloved celebrity after seventeen years in prison, risible. Darth Sidious gave the Trade Federation the keys to Naboo, then helped Amidala kick the Trade Federation the hell off Naboo. Even in the end, he wasn't showing Anakin a video-feed of Clone snipers with Padmé in their sights to get him to betray the Jedi, he offered Anakin something he wanted that no one (ostensibly no one
else, but really just no one) could give him.
It's like that "save the cat" screenwriter cliche? The villain needs to establish that they can participate effectively in criminal society, grow a following, maintain alliances. Luthor hasn't done anything for anyone, made a deal, passed a bribe, operated some kind of lucrative black-market, eliminated a threat, been decent company socially... all he's done is coerce people with murder-threats or actual murder. Presumably his entire organization is some kind of circular firing-squad where all his goons are themselves under threat of having their loved-ones murdered by his other goons, since we haven't seen anything that would make anyone willingly work for Lex. The closest things we've got, with Otis and not-Mercy, just seem to be deranged and personally obsessed with him. He certainly doesn't seem to treat them with respect, beyond simply glaring at them rather than handing them cell-phones connected to their loved ones who are tied up by strange gunmen whenever they annoy him.
As I said, he's not a villain so much as a monster. They're two different kinds of narrative threat, and the show is trying to treat him as a villain while only giving him the danger and unpredictability of a monster. There's a reason Oddjob works for Goldfinger, not the other way around.