League of Legends has several categories of champions, and the presence of each in your matches varies depending on different issues. Normally, players tend to opt for strategies that are most rewarded by the metagame.
However, there are always characters that remain in the background, without being able to gain popularity even when they are in good shape. In recent times it has become clear which are more affected.
The most boring champions in the game, according to a Rioter
August Browning, also known as Riot August, has served as Champion Designer on League of Legends. He's also never one to shy away from giving his personal thoughts on social media.
August's short answer about mages is that they weren't really bad, but "playing them doesn't feel right."
In fact, he confirmed his opinion with the status of the characters in ranked matches.
“In terms of their ability to win a game, mages are quite strong (…) However, playing them is not satisfactory and it feels 'outclassed'. The problem is that many of their actions are high risk and low reward."
He went on to explain that the fault was in the opponents, who make it feel like everything is much easier -- even if they give worse results in the long run. It's ultimately a situation generated by the more permissive playable patterns of these champions.
The hard part is that there is no easy solution to the problem, and League of Legends matches are drifting towards champions with greater sustain. Items and lifesteal mechanics mean that not everything is solved by simply increasing damage.
Ultimately, according to August, the problem is not that mages are bad, because that phrase would not fit reality. Simply playing them against certain champions can seem extraordinarily unfair, and that makes them, in a way, too boring. They just become wave-clear machines.
Fortunately, it is expected that with the problem being identified by the developer, they can apply changes that increase the popularity of mages down the line.
This category of champions was, for a time, the most beloved in all of League of Legends. However, issues with mana and its exponential scaling - coupled with a really weak early game -- have put them on the back burner for now.