Genuine Question: Why is League so Long-Lasting?

After the release of Concord, the hero shooter who would apparently rival Overwatch (and failed miserably), it makes me wonder why a game like League of Legends could last so long? Why are there no announcements of other MOBAs that try to boast themselves as the "League of Legends killer" like so many others do?

We had "Fortnite killers" and "Overwatch killers", but I don't think I remember any game claiming to be a "League killer."

Is it because of the F2P nature of LoL? If it is, why don't other games follow their model?

Is it because of their game design? What makes their game design better or more sustainable than other games of the same genre?

Is it because of their universe? With things like their Animatics, Music Videos, LoR, Arcane, etc?

I'd love to hear the thoughts of the community on this. I'm genuinely curious as to why this game, which is considered by many to be toxic and very much seen negatively by a good portion of the population, has lasted this long and is still one of the biggest games in the industry?