I make some of the partners, but also tend to go with townies or premades. I have a lot of incredibly pretty NPCs in my game, actually! I do go around editing most of my townies, but I never edit their actual facial features or skintone or hair/eye color or whatever. Often, once you put a different hairstyle and a nice outfit on a townie you'll realize that they're not all that ugly at all! I have to admit, though, that I am guilty of sometimes changing the body types of some of my townies... as I think they can get absolutely ridiculous. But honestly, I have some townies in my game that are just as pretty if not prettier than my own Sims!
Sometimes I'll also get unexpected couples between my own Sims - I play on a pretty long lifespan so only just been getting generation 2 going, and I wanted my teen Sim to have this romance with premade Max Villareal. Wouldn't work, unfortunately, so she ultimately went with one of my own played Sims with a story of his own temporarily but they turned out so cute together! :blush:
In my first save ever my Sim got along very, very well with gym trainer and premade Zoe Patel - so he ended up marrying her. Still consider them the sweetest couple I've ever had in my game, and their children turned out really decent. :smiley:
So, moral of the story lol: if you're feeling lazy and don't want to create your own Sims, the premades and even randomly generated townies can turn out really, really pretty with some basic editing (like hairstyles/make-up/clothing)!