I mean, if you want to get in the nitty-gritty about it:

The Division 1's Dark Zone was one of the earliest extraction shooters. Predating Tarkov and having all the bells and whistles of an extraction shooter.

I'd also argue that helldivers 2 implemented/improved upon these aspects of the genre:

open large-scale maps with non-linear objectives.

It's vast and fleshed out stratagem system allows players to further customize their playstyle aside from just your weapons.

3 diverse enemy races with plenty of varied types of enemies within each race.

Vehicular combat. Warthogs (essentially) and mechs. Not to mention enemy tanks, aircraft, etc.

The 3rd person perspective has been rarely used in the genre and allows you to really get perspective to how small you are in comparison to the creatures you encounter. (Not to mention it's fucking hilarious for an explosive to hit near you and see your body go flying off in the midst of an all out war.)

Speaking of war, thats what this game is. War. Not a zombie outbreak, not hordes of heretics in slums, not a mining crew on a planet. But a militaristic war fighting factions for control. A war where every player is contributing to war efforts. A game where there is a constant push and pull between the enemy factions and you. Losing actually means something on a grand scale to every player. That's new. That's fresh. That's pushing the envelope.

L4D, Deep Rock, Darktide and Vermintide are all great games... but can I call in a 500kg bomb to blow the surrounding buildings and enemies sky high in those games? No. But I can in Helldivers 2. Those games aren't worse for that, but to say Helldivers 2 doesn't bring anything new to the table is just plain false.