(note that I'm still in the early game, I picked it up two weeks ago and am on fall year 1)
I voted for relationships. The unique scenes that you get when your friendships are leveled enough are amazing, but the whole system is built in a boring way in my opinion.
You get an overwhelming introduction to NPC's through the introduction quest that asks you to talk to 28 different NPC's. Not only it's counter-intuitive because of the Wizard being the only "???" that you don't have to interact with, but the worst thing about it is you can't speak with shop keepers like Robin while they're working without going over the counter: it's a neat mechanic once you know about it, but for the purpose of the quest it's incredibly frustrating and it happened to me a couple times that I introduced myself to, say, Pierre and I'd be like "wait, but I've already interacted with this guy". Still, I've been holding on to playing the game because of how overwhelming it feels at the start - if you keep a gamer-like mentality that you have to follow quests it's going to drive you crazy.
Fast forward a month or two, you get your first unique scene with most NPC's around the 2/3 heart mark. On one hand, I'd like to get to know better the different characters, on the other hand, between their schedules and different tastes in gifts I feel like going after 29 different people two times a week is not worth it becuase it isn't fun.
Here's the thing, every now and then they make questions you have to give an answer to and it's kinda fine as a mechanic (but the questions I've got were not really that engaging), but besides that the NPC all tend to have repetitive lines of dialogues and making friends all comes down to you gifting them stuff, possibly their favorites. Birthdays give huge boosts, but naturally they go up slowly.
My friendship with Shane leveled up with me casually meeting him around and bringing him a salmonberry. My friendship with Sebastian is growing when I take quartz out of my chests to actively play Santa.
It all comes down to gifting. Make a checklist of what's liked by whom, fill your bag with the stuff and go look for them or look it up online. I think it's a very boring mechanic - not because of the gifting itself, rather because you have to repeat it two times a week for how many NPC you want. And you actually get to know them only after you have already gotten some friendship points. And apart from the events there isn't a single fun thing happening between each heart (yes, you get gifts from them in your mailbox, but that doesn't count as an interaction and you don't get to know them better and please Shane stop stealing stuff from the place you're working at).
I'm not far into the game enough to date or have a spouse but... I heard the character you marry isn't really flashed out, which is a huge shame.