Well, I used this opportunity to finally watch the last season.
Yui:
- sweet
- conventionally feminine, ideal wife material
- good social skills
- pulls MC out of his overthinking hole and gives him real socialization
- supports the man in his endeavors
- caring and considerate of everyone around her
Yukino:
- bitchy
- uses complicated male logic
- shitty social skills
- enables and engages in MC's unhealthy argumentation habit
- burdensome
- never listens to the man
- self-centered and withdrawn
The entire Yukino dating thing just felt off and showed how incompatible they were as romantic partners. I guess it was a little cute, but antisocial masculine x antisocial masculine just fundamentally doesn't work for romance, at most friendship and rivalry. Out of the three, Yui is basically a requirement.
Hachi x Yui would work, but let's be honest, threesome ending was how it was clearly meant to be all along (+cheating with Iroha when he needs to blow off some steam). S2 ending with the double date had overwhelmingly best vibes. Yui cares about Yukino and Yukino appreciates her support. They all bring their strengths to the relationship, leaving either one out of the loop just doesn't feel right. The 2023 OVA saved things a little, though it only hinted towards love triangle (which still has the possiblity of ending as threesome) and felt rushed overall.
Well, you could say (even though he clearly enjoyed most of the time spent with Yui), that he still didn't really love her, but that's a HikiGAYa issue of not noticing her supreme qualities.