We didn't learn much more about Sylvie this season.
Well considering her arc was mostly completed in season one, there wasn't much more TO learn. We knew she just wanted to retire to a branch timeline and experience life in a way that she couldn't when she was on the run from apocalypse to apocalypse nearly all of her life, and given how long Asgardians live, that could've been centuries. She just wanted to enjoy life and its simple pleasures, from fast food to vinyl, and her purpose this season was to get Loki to realize what it was that he really wanted.
We didn't learn anything about B-52 or whatever.
Hunter
B-15 was a doctor, presumably for children, with a lot of empathy and compassion, which probably influenced her judge of character and conviction to save the branch timelines from being wiped out once they learned they didn't need to prune them all. Learning who she was on the sacred timeline really put a good spin on how she's been viewed since Season 1 and rewatching that with this knowledge could spotlight some of her character moments.
We didn't learn much about Renslayer that wasn't heavily implied last season.
I'll agree, her arc this season felt a bit underbaked, though the revelations of her involvement with He Who Remains put her in a peculiar spot, and considering we didn't see Alioth consume her, it's safe to say she's still alive and probably has plans in the future, either to get revenge against Sylvie, the TVA, or HWR. She was really just a pawn for HWR and Miss Minutes this season, though the revelation of her story with Mobius really explains a lot about her ruthlessness, especially concerning Sylvie.
We learned nothing about Victor Timely.
We learned he was a no-name candlestick maker in the late 1800s, who might have influenced OB to write the TVA handbook. He was a brilliant con artist, which isn't too dissimilar from how Kang might operate, but he definitely shows that Kang Variants have a lot more variety than just being a green-and-purple-clad villain. I guess if folks found him annoying, they weren't going to glean anything from his character, but for those of us who enjoyed him, there was a bit to learn.
We learned little about Mobius other than what his prime timeline guy was like.
I feel like Sylvie, Mobius' arc was mostly complete in s1, but seeing his friendship grow with Loki was a key aspect of this season. There's a reason he's with Sylvie when they see Loki approach the gangway. Those are his closest friends and they motivated Loki to make his final decisions at the end of the season. The repetition of the "For you. For all of us" line from the end of the first Thor film, but this time to Mobius and Sylvie, really hits differently now, and was a brilliant inclusion in those final moments, along with Mobius' line of "Most purpose is more 'burden' than 'glory'.", which is just so beautiful, and a great twist on Loki's typical "I am burdened with glorious purpose." line he's said many times.
We also learned nothing about OB.
He was a failing sci-fi author and physics professor, which explains his aloofness and genius intellect, and seeing how his lab on the sacred timeline clearly inspired his TVA lab, it feels like when he joined the TVA, they either didn't erase his memories or his memories remained in a hazy way that kept them from being completely erased. Beyond that, I don't think we needed to learn much about him, as his presence was to create tension in the plot ("We're all gonna die!"), provide some curious puzzle pieces (learning Timely inspired him to write the handbook, which inspired Timely, etc), and ultimately help guide Loki through his time-slipping journey. Like the others, he survived and so there's a chance we may see him again, but honestly, I don't see a reason to need to learn MORE about him - just let him be a quirky tinkerer. Not every character needs a super in-depth backstory full of intrigue and drama.
I loved all of the actors, Ke Huy Quan was fantastic but ultimately just a means of exposition. Loki's arc from Thor 1 to this (not counting his other arc) is great, but this season just felt like stuff happening and I really didn't connect with it. I didn't hate it, I just kind of felt nothing. Glad others enjoyed it though.
Looking at Loki's arc from 2011's Thor up to now, it's amazing seeing what he became, both on the sacred timeline ("You wlll never be a god"), and at the TVA ("I know what kind of god I need to be."). I'd say his story is probably one of my favorites in all of the MCU now, next to Stark and Rogers, who, of course, have had definitive endings in their own right. If we never see Hiddleston's Loki ever again, I'd be satisfied, but I wouldn't turn down another glorious chance to see him on screen as long as his purpose for being there wasn't a burden.
-Marc.