But think about it. Sith were VERY prominent in the prequels and we learned about "The Rule of Two", a rule designed to be broken so that masters are killed by their own apprentices
By the OT, Vader did not had any apprentice, and the Inquisitors aren`t Sith apprentices just Hunters, Palpatine did everything in his power to put Vader on a short leash so he wouldn't get any apprentices (Because fuck TFU lol)
So if Palpy and Vader died, who's going to be the Master? The Dark Side is still there sure but it would make sense if the Sith Ideology is lost forever as Palpatine hoarded knowledge and hid all kinds of info about the force, like the existence of Midichlorians.
I like the Sith a lot, but it kinda makes sense that they are gone to give rise to a new kind of Dark Side users. Which is why I kinda want the fanboy/wannabe angle. Just like Neo-Nazis