People expect a DLC provide them 100s of hours of new/fresh gameplay that will allow them to play the same game for 3-6 months until the next DLC release. Comparatively you could look at the same amount of content and play 50ish hours of game play then set it down and play something else until the next DLC. Even though my play style is closer to the former, I think the expectations of the latter are more healthy. This mismatch of expectations and the pricing of any DLC (which adds in macro factors outside of the Dev's control) has lead to such toxicity on the subreddit at times.
It's also interesting how much that toxicity has subsided in recent months with positive releases, better/consistent developer correspondence. Which maybe points to my expectations opinion being a bit wrong.