It irks me a bit when I see "why did so and so score so low", it's popularity not who deserves it. TD just feels the most out of place to me, don't get me wrong I love Miko, seiga, and yoshika but I keep repeating myself... 7 I have to choose 7. It could also be the fact most of TD's characters we know a lot about already. Take Rumia for example, what is she? What kind of youkai is she? She still has mystery to her so people are still interested in seeing more of her. Wakasagihime scored in the 60s, but I love her! Her design... and that's it really... I mean she's nice and part of a group with Kagerou but there is nothing else I know about her, I want to know more about her and only the fandom can fill that need.
I don't know those are just my thoughts about TD.
And I'm the complete opposite. I can't get myself to like characters with not much information about them, like Rumia, Kagerou, Momiji, etc. precisely because there isn't much I could like about them! Sure, there's all sorts of different interpretations by the fandom, but I'll use Momiji as an example here. A good portion of Momiji fans only like her for the Awoo, and I find things of that nature to be annoying. It's a similar reason as to why I don't like all the partner pairing shipping nonsense. Things like Doremy/Sagume have no logic behind them and I just don't see the chemistry in many of these ships.
On the other hand, I do like characters such as Marisa, Aya, Tenshi, the Komeijis and the Scarlets because it's clear enough what kinds of characters they are as well as the relevant plots and backstories involving them. Memes aside, I do see why these characters are very likable by large parts of the fanbase. There's also a reason why Reimu/Marisa is the dominating pairing - it's because they're both featured the most in terms of playables, and thus by looking at how either of them handle the incident through the various games, the logic is obvious. Pairings like Marisa/Alice (no, NOT the clingy Alice) and Reimu/Yukari also make a lot of sense due to this.
My favorite game is SA, by the way. I'm not saying the other games are strictly worse. In fact, I don't find any game
bad, per se. It's just that I prefer specific games over others.