At this point, DOTA2 actually does have plot when compared to League.
When was the last time you played it? Beating the tutorial unlocks a special book that contains various information about the game's world and an epic poem about a minor item, and every character has a huge multi-paragraph story. Plus every single set of cosmetics has its own lore about how it was created, and sometimes additional lore for how it was obtained by the hero (Rylai's Frost Avalanche and Mortred's Manifold Paradox both have that).
That's pretty much why Riot's decision to delete the lore and reduce it to promotional trailers in this particular season is so embarrassing. I don't know if you've been following news, but among both existing and future MOBAs, only Gigantic doesn't have some sort of narrative content attached. And even Gigantic has lore, plus it has an excuse of still being in alpha; they're busy finalizing the game itself.