All non-premade sims are aromantic and asexual?

@Rambling_Rose314What I usually do anyway is to create a few townies of my own and keep them as future possible partners for my Sims. Sometimes I create my Sims in say, a flat share and then move them out. I move the "spare" Sims into Other Households but my Sim has their friendship with them so if I decide to start a relationship with them they have a head start. They don't even need a house, you can move them out.
I also add a few random solo Sims or pick a few NPCs in Other Households and edit everything about them, again to make them more suited to my Sims. I tend to go through Other Households regularly, culling random NPCs and editing others or adding some of my own.
So that's just an idea to make relationships a little easier for your Sims. You mention Legacy there which I don't play, so maybe the second option is better for you.

I started playing in University dorms where basically every roommate is a randomly generated sim. Litterally everyone of them is aromantic and none of them are exploring in my savegames. (I tested with and without mods in 3 saves and it happened in all of them). To say this is annoying is an understatement. I am pretty furious cause my entire uni gameplay is now boring af. No drama what so ever! And uni roommates in dorms cannot be choosen and editing them usually makes them dissapear as roomates. So the solution from @simsplayer818 cannot even be applied here plus roommates in dorms change weekly. Despite it beeing unrealistic that every sim is aromantic, I shouldn't have to import sims into my saves for my sims to be able to find love after a few generations. And I don't want all my sims be in a friends with benefits relationship as nice as it is to have the option for that now, but I wanna at least have the option for more with at least some randomly generated sims.

@LuchsArcanaI've actually had issues with NPC students too, before the recent changes when living in a dorm. It's a weird one, dorm life. I had loads of random students acting weirdly and not really part of the game. I ended up editing Briny Tower and making it a solo apartment for my Sim, Malin. I then took a student I recognised in Other Households, and edited him. I brought him into my game briefly. His uni info all disappeared and I had to re-enroll him and make him somewhere to live. I introduced him to Malin once he was set up with his life. I then went back in to Malin's game and she was happily dating him.
If you move them to a dorm and then to Other Households again, they often inexplicably vanish. So it seems its the dorm that's the problem. It acts in totally different way to other residences. It's just weird, I can't explain it. I stopped playing dorm life and it's a real shame. Time slowed down because Sims never stopped moving, they were producing food from thin air and dumping it all over. Stuff broke and build mode wouldn't let me edit it. So I just use residential mode instead. You can use Darkwing House (if I remember the name right) set it to residential and create a house share to get the college co-ed experience as a substitute for the dorm. It's still on campus so you're still part of the life. Or do what I did with one of the towers instead and again, switch to residential lot type. If you don't want to play all of the Sims in a residential group of students I guess just change the autonomy settings. You can apply for room mates or create your own, or find students you recognise in Other Households like I did.
I'm on console so I don't know if there are other ways to mitigate the dorm life weirdness on PC with mods. I actually enjoyed doing it this way after sooooo much hassle with it led me to my solution.
Good luck!

i’m having the same exact issue. and all the sims say they’re open to exploring but they turn down my sim. i don’t even have the option to become woohoo partners. i’ve been trying to find someone else who had this problem since the update came out, i was so excited for this inclusivity but it has made the game unplayable 

I feel like it’s a sort of Schrödinger’s cat situation. They have no orientation until you ask them… but when you ask them it locks in. If I use the ask about woohoo preferences option or push too far before I’ve flirted enough to get an NPC interested, my Sim will learn they’re not interested and that becomes a permanent orientation. But if I don’t ask, and just do a whole bunch of low level flirt, ask risqué question, etc. until they’re flirty, then their orientation turns into whichever gender my current Sim is.

So…just stop asking about Sims’ orientations? If you don’t ask it doesn’t block you. 🤷🏼‍♀️

I have this issue only with new saves but there I use now flauschtrud mod, which fix this thing.

In my old save my townies get created as it should be. Romantically attracted is empty, exploring is on yes, and WooHoo interest is in both.

In my new save they always end with romantically attracted No, exploring No and WooHoo neither. So, I got a bunch of Asexual/Aromantic sims which will not change the sexual preference because exploring is on no. So, the player need to edit all created townies in vanilla and change exploring to yes and change interest in WooHoo if you want to WooHoo.