Seems like there are some unspecified assumptions here. For one, an assumption that TLS is the only game in town. Another is that "you", as in "you must do this" or "you must not do that", applies to every person equally,
When one uses TLS today, chances are very good that it's using something from djb, someone who "made his own crypto". Maybe the assumptions, stated as "rules", do not apply equally to everyone. For example,
"And if you wanted to implement all that yourself, people will yell at you for doing your own crypto."
In fact, before HTTP/2 existed, djb did exactly that, as a demonstration that it could be done.^1 It succeeded IMHO because it worked. People can "yell" all they want, but as above, these same people if they use TLS are probably using cryptography developed by the person at which they are "yelling". Someone who broke the "rules". Perhaps there is evidence that HTTP/2 would exist even were it not for the prior CurveCP experiment. But I have yet to find it.
The word used in the parent comment was "implement" and the suggestion is that attempts to "implement" would not succeed. Perhaps the reason they might "fail" is not a technical one. Perhaps "success" in this instance really refers to acceptance by certain companies that are making "rules" (standards) for the internet to benefit their own commercial interests. It may be possible to implement a system that works even if these companies do not "accept" it. If so, then the problem here is the companies, their fanboys/fangirls (watch for them in the comment replies), and the undue influence they can exert, not the difficulty of implementing something that works.
IMHO, getting something "accepted" by some third party or group of third parties is a different type of "success" that getting something to work (i.e., "implementing"). It's the later I find more interesting.
1. https://curvecp.org