BE isn’t technically dead buts it’s practically dead for almost all projects. You can static_assert byte order and then never think about BE ever again.
All of my custom network serialization formats use LE because there’s literally no reason to use BE for network byte order. It’s pure legacy cruft.
...Until you find yourself having to workaround legacy code to support some weird target that does still use BE. Speaking from experience (tbf usually lower level than anything actually networked, more like RS485 and friends).
18 years in my career and I’m still waiting for that BE target to rear its ugly head.
I’m more than happy to static_assert little endian. If any platform needs BE support then I’ll add support to the minimum amount of libraries necessary to do so. Super easy.
Here’s the thing. If you wrote BE compatible code today you probably dont even have a way to test it. So you’re adding a bunch of complexity and doing a bunch of work that you can’t even verify is correct! Complete and total waste of time.