I think you are missinformed. There is free content with every single DLC and the DLC is way more than just new factions (cultures). There are new type of leaders, new mechanics like the forge to build your own artifacts, and new magic tomes which is a fundamental part of the game that help you change/customize your culture in very drastic ways (major transformations like converting you in demons or undead). .
They added a whole new map level (the umbral abyss) with their last expansion as well as a complete overhaul of the Mystics culture (as free content too) adding 3 quite different options to play as (and it is rumored that they may end up doing the same with the rest of cultures).
They definitely added new units in the paid content, I'm fairly sure also some as free content but can't remember which exactly. Not to mention less important stuff like new mounts or hero customization (most of it free).
With the first new expansion in this season pass they are introducing a new renown mechanic for your heroes as general free content too.
So the content of the expansions is quite varied in my opinion and there is quite a good amount of free content coming with it. I may agree that even though it has these story realms it does not provide a proper campaign but this is a design choice from the base game so not fault of the expansions.
I get you don't like the content, ok, but I don't think there is the need to complain just about the fact that they are releasing new stuff as a concept, which is what I got from your first comment.
Yeah but there not true story campaigns. You pick the scenario/realm and make your own story in a sandbox. Your creating your own godhood origin. That is the whole story.
To say the truth I wouldn't know. I've played a lot of this game and still didn't started a single story realm. I hardly play campaign in these type of games because normally it sucks (a lot) in the gameplay department. I know some people like it, and specially here in an RPG site you might be the majority, but I'm not sure if that is the case with the overall audience of these type of games.