I get the point you're trying to make, but making everything custom adds cognitive load that isn't necessary and restricts your design space. The more time you spend thinking about your custom solutions, the less time you can spend on features that differentiate your product.

I had to troubleshoot an issue that a higher up in the company was having with their bridge at home. I asked him to hit a specific endpoint on his bridge in the browser and send me the result, a win for HTTP.

We just released swagger docs for internal devs and 3rd parties to plug into without needing to spend time writing excessive documentation on what our data format look like, a win for JSON.

The list goes on for all the extras you get for free when working with standardized tools.