@Riot: Champions don't get played because they suck.
Popularity depends heavily on perceived viability. Most of the time the perception is true.
I keep seeing Riot posts explaining why a given champion isn't satisfying to play. I think it's complete BS. And hear me out because I've been playing this game for 5 years. I've seen every champion rise and fall.
Let's look at some examples.
- He used to be completely different in appearance and lore. He felt totally different. Riot gave him probably the most drastic VU any champion has received. They said it would make him more popular. It did for a short time because the new Trundle was, well, new. However, Trundle did not prove to be more viable just because more people played him. He has never been a top pick in the competitive scene before or after his VU. The VU failed to significantly improve Trundle's popularity. He fell into obscurity when the novelty wore off.
- Similar story as Trundle but her VU was not as drastic, and she got more significant changes to her gameplay and tuning. She was considered a strong pick after her changes and she was popular for a patch. She was nerfed and fell back into obscurity, once again showing that the VU didn't help her popularity, nor did the changes to her gameplay. She needs to be viable/strong to be popular.
- Before Sion's remake, Riot said that his gameplay wasn't satisfying. They could easily make this claim due to his low popularity. The truth is, once upon a time he was a very popular champion because he was strong. Two things happened. AP Sion was nerfed (deserved) and the game power creeped past AD Sion. It got to the point where he just sucked in lane and was too frustrating to play. So he fell into obscurity.
- Even Galio was considered strong at one point, and he saw a lot of play. What really hurt him was a nerf to the damage on Righteous Gust. It was considered too reliable for harassment so they nerfed it to make him depend more on Resolute Smite. With his harassment (especially against ranged champs) less reliable, and his unreliable engage later in the game, he proved to be an unreliable pick. Even in a mage heavy metas he never caught on because honestly in lane his kit works best against melee champions due to being able to punish them for last hitting with Resolute Smite. You could go into all kinds of reasons why you think his kit doesn't "feel" good but you can really only speak from your own experience. I and other players do enjoy his kit but personally I haven't considered him a strong pick for 2 seasons because of problems with his laning and his engage. I think the addition of Righteous Glory helped him a lot this season so I'm actually going to try playing him a bit, but that's beside the point.
- Garen was considered weak/outclassed and his popularity was declining. Then he got a VU and was popular for like a week. Then people dropped him again because welp, he still sucks. Honestly he's a pretty fun champion IMO but I wouldn't be caught dead playing him. I like to win.
There are also examples that go against my point like Vayne, Lee, Yasuo, etc... Champions that a lot of players find really fun regardless of their viability. You will see these champs played even when the meta does not favor them. The thing is it's pretty hard to force this. Riot has failed time and time again with VUs and remakes to repeat these successes. They are accidental. Most of the time a champion needs to be viable/strong to be popular.
I believe there are a lot of players like me who will avoid champs that we lose often with. I wouldn't be surprised if most players are like this. The problem with a weak pick is usually it's due to bad lane matchups. The game is not fun when you are losing your lane because you feel powerless. You can't do anything but try to salvage the ruined lane. Chances are the game won't get any better for you because your lane opponent will snowball. So anything cool about the champion you're playing doesn't matter because you're just sitting there watching other people have fun on their champions. So maybe the champions that people like despite their viability are the ones that avoid this in some way, like if Vayne loses her lane she can still pull off some BS and kill somebody mid-game. If Lee does badly in the jungle he can still use his utility to make plays or even get kills with his Q execute. The fact is most champions suffer a lot when they do bad early so whatever cool stuff they have doesn't matter in that case.
So like I said about Galio, there are going to be players who enjoy any given champion. We all have a different mindset on how the game is fun. LoL is a good game because it offers so many different experiences. So it's a mistake to look at a champion based on your personal idea of what is fun and try to make it seem objective with a bunch of analysis. Realize that there are a lot of different players who like different things, but most of us are going to gravitate towards what seems to work because the cool things about a champion only shine through when the champion is viable.