What's with the performance obsession of today's generation of programmers?

Most software applications are not performance-sensitive. That's why languages such as Python, Java, JavaScript, and R continue to dominate.

Is software ever fast enough? Where do you draw the line? What is the threshold of acceptable performance?

Yes, there are some fields where performance is a significant concern. Computational science is an example.

But there are many fields where performance takes a backseat to other more important considerations, such as productivity, ease of use, and scalability.