Hm I can see where you're coming from in regards to Bolin and Opal, but yeah, I just didn't found any of the romance in LoK that great. They didn't handle romance very well this time around, which makes sense, since LoK is a mini-series and they didn't really get the chance to blossom the relationships over a longer period of time, which is understandable.
Yeah, I absolutely love Korra, despite my grievances with the ending. I still love ATLA more though, but they're both amazing series in and of themselves. And I agree about the ending part, it was nice to see that it was mostly focused on everyone else, but like I said, I really wished the ending was different because I wanted an ending that was more inclusive, I guess?
And there were a few subtle hints over the 2 seasons sure, but it just didn't work well with me because it seemed like the most unnatural relationship in LoK. I would also like to point out that I am supportive of the LGBT community and I'm stoked that they've "pushed boundaries" by showing a same sex couple on screen, but I just didn't find their relationship natural, regardless of the 3-4 hints in the last 2 books. If you compare Korra to Mako, they had many interactions with each other before they were "official", but even then, I didn't find Korra + Mako a good paring. I guess I'm just not into the romance aspect of LoK. And regards to the "religion" thing, I'm not sure what you mean? I didn't mention anything about religion so I'm a bit confused.
And yes, there are defo a lot of memorable characters but I think the dynamic between Verrick and Zhu Li was the best!!
Btw just wanted to say that I'm not against what you're saying at all, just throwing in how I feel about the show just so you can understand why I "diaspprove" (wrong word to use) the ending. (you need an account to see links)
ANYWAY, enough about hte things that I dislike about it, LoK overall was great and I'll miss the Avatar-verse so much ;~; I've still got the comics to read though but that won't last long enough for me either. ._.