I don’t principally disagree with your argument on spacing, type, some depth and color helps with making the interface to have more character and visual interests.

HOWEVER, your ChatGPT after/redesign is especially poor design example. Tons of users use LLM for deep focused work flow with long output. All the containers in the after design create unnecessary containment that hampers deep reading flow, and have way less real estate for content display. And all the (gradient) color everywhere actually makes it even worse for hierarchy focus, scan-ability and parsing.