How important is zooming in and out (cmd + , cmd – ) for websites (Desktop view) in terms of accessibility?

I am working on a website at the moment and someone else is in charge of the HTML/CSS side of things.

I've noticed it's not possible to zoom in and out with the browser function of cmd and + or -. The website just rescales instantly due to the css.

I don't know how important this feature is in terms of accessibility. Do people with strong impairments of vision use it regularly or are there other use cases I am not aware of?