Of course everyone is taking ideas from their competitors, the goal of the tactic is to make the player base not feel robbed of features or ideas that are implemented by the competitor, so everyone is stealing from each other. This always happens, this is natural, and, arguably, this is very good for the players.
It is actually pretty bizarre its all become near interchangeable at this point.
LoL/Fortnite: Easier you get into, More popular, gets accused of being the "for kids" version, Gets accused of being a copycat
DOTA/PUBG: Harder barrier of entry, Huge community but can't quite reach the audience of the competition, claims to be the more " for adults" game, Both have original devs that popularized the genre.
Both communities having pretty intense tribalism and refuse to play the other and both games despite the arguments have huge skill ceilings in exact same manner.
If you wanted you wanted to go even deeper HoN/H1Z1 also pretty much played the exact same roles in the respective genres aswell and they both have have/had clones trying to find their niche. Both also came from niche mods ARMA(BR) & DOTA (WC3)
History literally repeated in two completely unrelated new genres, its fascinating.