Container isn't responsive to portrait mobile layout

Much of my website uses the built in Containers to get a responsive sized div that doesn’t span the whole width of a desktop screen. However, now that I’m getting around to making the mobile layout of my website, I’m noticing that the container doesn’t shrink small enough when in mobile portrait mode:

Do I have to redesign my whole website to use divs instead of containers for content? That would be a huge pain. I thought containers were supposed to fit the screen!

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