There are diegetic elements like that, but also how the non-diegetic HUD delivers information.

When is it giving information? Is it giving me information I don’t actually need at the moment. For example a first person game that always has a compass or minimap. Maybe I want those sometimes, but do I want them always?

What are the visuals of the HUD like? Are they easy to read? Are they distracting? HUDs that have stretched and difficult at a glance fonts are a bad idea to me. Simple fonts that can be read against a variety of background colors are seemingly underdesigned to many UX designers, but it’s all I want sometimes.

Do HUDs have needlessly animated elements? Sometimes just putting a plain and simple number or bar on a screen is enough, but many games add so many artistic flourishes that it gets in the way of the game visuals.

HALO CE had its shield bar with the little health dots underneath. Technically diegetic, but obviously a gameplay element. It wasn’t distracting, it was clean and easy to read, it gave information that was constantly relevant.