Hi there Adam,
Taking another look at your site, I see that you now have a “Next step” button that you can click (instead of clicking the billing section at the top):
Link to image: https://d.pr/i/JFKAyj
You had mentioned that you would prefer the default Checkout rather than the Stepped Checkout. To clarify, the default is just to have the Billing / Shipping / payment all on a single Checkout page, rather than clicking through different steps like your Checkout is currently set up to do.
Taking a look in the browser dev tools, I see that the styling on those checkout “steps” appear to be coming from your theme:
https://harvbocards.com/wp-content/themes/thegem-elementor/css/custom-LNpx2QOb.css?ver=5.5.3
I would recommend reaching out to your theme developer to ask about changing this (they may have a setting to disable the stepped checkout).
You can also try temporarily switching back to the default Storefront theme to see how the default Checkout might appear (you may also need to disable the Elementor plugin to see that).
I hope that helps!