That fails pretty hard at providing a rationale. Basically it says that CGI is an inefficient interface because it involves creating a new process! Even if that were true, "You shouldn't want to do such an inefficient thing" is very, very rarely a reasonable answer to a technical question like "How do I write a CGI script in Python?" or "How do I parse a CSV file in Python?"

There are certainly some suboptimal design choices in the cgi module's calling interface, things you did a much better job of in Django, but what made them "near-impossible to fix" was that at the time everyone reading and writing PEPs considered backwards compatibility to be not a bad thing, or even a mildly good thing, but an essential thing that was worth putting up with pain for. Fixing a badly designed interface is easy if you know what it should look like and aren't constrained by backwards compatibility.