There are a couple of problems at play here really. I don't think ALL your protocols and software need to be designed as The Right Thing, for the reasons that y

There are a couple of problems at play here really. I don't think ALL your protocols and software need to be designed as The Right Thing, for the reasons that you already outline - time to implement, brains required, market penetration, etc. What needs to be designed as The Right Thing are protocols that implement important infrastructure for the society as a whole. Sure, SMTP and DNS are important infrastructure for everyone now, but at the time of design they were far from it, and I don't think the original RFC writers can be blamed with going the "Worse Is Better" route.