Why can't I customize my checkout page?

I can’t get to customize my checkout page.
This is what I get when I try to get into customizing it.
Settings → Checkout and accounts → customize checkout
This is what I get:

Hi @Idan3 ,

Thank you for reaching out to the Community! I’m happy to provide some assistance with theme customizations, to ensure this gets resolved. To confirm I’m fully understanding, are you looking to make edits to the shops cart or checkout page?

To provide some insight, adjusting or editing the checkout is beyond what’s possible using the Theme Editor, our Theme Support, or Shopify Experts. The checkout is a secured page, where the code is not made available. This is to help ensure that the information for both our merchants and their customers remains safe at all times.

While I can completely understand the impact, this decision helps to ensure that the information from both our merchants and their customers remains safe at all times. For more information on this, you can check out our PCI Compliance documentation as it touches on this further.

If however, you are on a Shopify Plus subscription plan you can gain access to the checkout extensibility to customize this page. For more details on this, you can refer to our Customizing And Editing Your Checkout documentation.

Please let me know if you have any other questions or concerns.