Yeap, the DLCs seem to just get in the way most of the time. They add a bunch of mechanics that don't gel well with the base game, the worst being the Urkan. Some of the factions are also very one-dimensional and it's obvious they didn't have much of an idea what to do with them. The underwater one (which is overpowered btw) and the white floaty one particularly come to mind. Even then, I'm not exactly sold on the different factions in this game. My problem with them is that they all come with different mechanics that mostly they use but aren't integrated well with the base game. Compare that to Gladius' factions where most faction mechanics exploit base game features to put a spin on them, even though some of them come with unique mechanics which aren't in the base game (Webway Gates for both aeldari factions and Holy Sites for the sisters). Some new mechanics aren't bad, but EL goes overboard very fast.
The base game's idea for different and actually unique factions was very cool and easily its most distinguishable feature, no matter which way you want to spin it. They also weren't impacted as much by this entire notion of mechanics that can't really be used because AI doesn't work with it both when you play as a faction or against it. Mostly concerned the draconian diplomats.
Even the add-on factions don't sound that bad on paper tbh. It's just that those come with the global additions that tend to range from "what were they even thinking" to pure cancer. And it's definitely a pattern, because ES2 was EXACTLY the same. I swear to god, I'm a nice guy, but if I ever meet the person who came up with the hacking "mechanics" I'll sucker punch them in the crotch real hard.