Non-clincher tyres predate clinchers. Clinchers rely on a hook and bead (and hoop stress) to keep the tyre on the rim with high pressure. Non-clinchers where low-pressure jobbies that went with shallow, non-hooked rims.
If you say you've never had a problem with open-bearing BBs, I can't argue with that. I sure as hell appreciate the work done by seals and the grief it saves me.
When I was at school, my science teacher had two bits of wisdom on the wall. The first said: Good enough is never good enough. The second one said: The secret to success is hard work and that's why it will always remain a secret.
This stuck with me throughout my life and therefore, good enough is just not good enough. But, I'll give you the opportunity to explain why a quill stem is "great".
Bikes that have different roles e.g. racing, shopping, commuting, touring have different criteria for "good". For shopping and commuting good enough covers comfortability, reliability, efficiency, often price. If the cranks turn around smoothly, are not made of cheese, and can be maintained easily then that is "good enough". Even for racing "good enough" is OK as long as it is better than your competitors.
In a practical sense good enough, at any level, depends upon performance needs, and is a balance between quality and budget. That shouldn't and doesn't stop development and improvement, and good enough for a racing team has to be miles better than good enough for popping to the shops.
While I love the modern stems/headsets for their ease of headset adjustment and maintenance, and probably their looks on a modern frame bike, especially mtbs, I also like the look of quill stems, especially on old steel road bikes. I like the ease of changing the height of the bars without changing stems or spacers. Quill stems have their problems, especially the faff of changing bars, and the fact that if left too long they can stick in the head tube. But that's due to faulty maintenance.
The good thing about technical improvements is that they don't necessarily make redundant the older technology for fogies like me.