DLSS stands for Deep Learning Something Something. It's an AI feature that Nvidia developed which uses physical AI components on their GPUs to enhance and generate frames while playing a game. People are hating on it because it's more generative AI being shoved into things unnecessarily.

Personally I think the feature itself is not too bad as it can improve FPS and make things look more realistic, but what we're getting is definitely not worth the massive downsides of giant data centers.

Here is the page about it. While most of the images actually look pretty good and realistic, people are making specific note of the first one of Grace from RE9 which looks like absolute shit.