You are being over the top and quite frankly ridiculous. I've been using .Net Core in production since its initial release while working for a famous games company (which you probably heard of) and now for a multi billion dollar FinTech firm, and the whole time I have been using HttpClient or libraries using HttpClient for connecting to services/apis.

If your whole reason for not using .Net Core is based around this weird and honestly unimportant edge case, all that tells me is that you have a strange bias against the framework for some other reason and looking to nitpick.

Modern workloads refers to the kind of applications commonly built today, like http/json/grpc webservices running in containers.

And yes the HttpClient is modern. Your entire argument so far has been a single RFC issue that is labeled up-for-grabs because it's so minor and doesn't really affect anyone. Claiming the http functionality and the whole stack isn't modern because of it just doesn't add up.

That "8 year old standard" you linked to is just a draft and proposed standard. Nobody implements draft specs in production grade libraries/frameworks. Especially not Microsoft.