> any minivan on the market is going to do an acceptable and safe speed

Growing up my folks had an old Winnebago van that took 2+ minutes to hit 60mph which made highway merges a white-knuckle affair, especially uphill. Performance was a criteria they considered when buying their next minivan. Whereas modern minivans all have an acceptable acceleration -- it's still important, it's just no longer one you need to think about.

However, not all modern interfaces provide an acceptable response time, so it's absolutely a valid criteria.

As an example, we switched to a SaaS version of Jira recently and things became about an order of magnitude slower. Performing a search now takes >2000ms, opening a filter dropdown takes ~1500ms, filtering the dropdown contents takes another ~1500ms. The performance makes using it a qualitatively different experience. Whereas people used to make edits live during meetings I've noticed more people just jotting changes down in notebooks or Excel spreadsheets to (hopefully remember to) make the updates after the meeting. Those who do still update it live during meetings often voice frustration or sometimes unintentionally perform an operation twice because there was no feedback that it worked the first time.

Going from ~2000ms to ~200ms per UI operation is an enormous improvement. But past that point there are diminishing returns: from ~200ms to ~20ms is less necessary unless it's a game or drawing tool, and going from 20ms to 2ms is typically overoptimization.