It’s really rare to find a game where the protagonist is a female and the males are not ugly and old. I just find 2 games like that
Unsurprisingly, considering her own father was pretty much absent through most of her childhood, Anna has definite 'daddy issues'. So her being attracted to much older men is probably a consequence of that. And it's nothing new. She fancied one of her teachers and she fancied her boyfriend's father ( the flashback at the hospital makes that clear). She may have even idly fantasised about her own grandfather, which demonstrates she's not only turned on by good looks, but maturity and experience as well.
Also, you need to consider that her condition is making Anna into a classic nymphomaniac. Women like that don't really care about looks, all they care about is scratching that itch that never goes away. She's gradually becoming insatiable and unable to resist temptation whenever it's offered.
In addition, the Dev is trying to appeal to a wider audience. Older men like it when the female protagonist willingly fucks men just like them. And Deep himself is on the older side, so it's not really that surprising that he wants his heroine to have a thing for older guys. He's never made it a secret for instance, that he gave Anna a really big butt, because he's turned on by women with big butts. Why should this be any different?
Fortunately, Anna is still attracted to younger guys and good-looking middle-aged guys like John, so it's not like there aren't plenty of options to the older guys like Alfred and Benjamin. Plus, it's very easy to avoid all these older guys if you particularly object to having sex scenes with them. In most games of this type the female protagonist actually has sex with less than a dozen different characters, so even if they all were young and good looking, Anna still has sex with more of this type and just as frequently, because this game just has so much more sex in it, than virtually any comparable game. Therefore, if you so choose, you can avoid all the 'old and ugly' guys, and still have enough sex scenes to make this game worthwhile.