Some of my main issues with the new lore when compared to the old is that it focusses way too much on certain characters (especially Jaina and Sylvanas) and not enough to the actual world. And it doesn't feel like they are expanding on the world enough with new material, but rather they either recycle what we have done already (Suramar is basically Silvermoon 2.0 in that regard), or they just retcon already established lore in favor of introducing new characters (the Jailor being the mastermind all along while every other high ranking Scourge leader was apparently just a pawn), or when the writers just want to push their own story which in return hurts the older lore.
Now compare the RTS games. WC1 and WC2 are basically the same game (with some technical differences ofcourse), but in its core you have the good guys vs the bad guys. The lore itself is very simple and it worked. You had a lot of characters who played their roles, and the important part is that most of these characters also had a fitting ending for their arcs which allowed for WC3 to come up with new stuff. Basically the only few characters who came back in WC3 are Uther and Grom, and they too played a proper role that allowed the game to move forward and develop their newer characters. In return we got Arthas, Jaina, Thrall, Tyrande, Malfurion, Sylvanas, just to name a few.
But then we get to the problem that irks me to this day. In WoW we haven't really gotten much out of these characters in Classic and TBC which was fine for me, the game was based more around the world and player characters. In WotLK we saw a continuation of the Arthas story and gave him a proper ending. But then starting with Cataclysm, they started to use all of their WC3 characters in major roles, overshadowing both the world and players and most of the time they get portrayed as way too powerful with too much plot armor. And this is still a problem that we see today, we are still stuck with seeing WC3 characters do basically everything while WoW itself failed to deliver new characters.
In WC3 we had the characters from WC1+2 move on and they introduced new characters, WoW failed to do the same thing and is to hung up on the characters from WC3. Thats not even to say that they have to develop all kinds of new characters for the spotlight, because as a MMORPG I would have loved to see the world play a bigger part instead, yet it doesn't feel like WoW is delivering any of this.