I think there are circumstances where it is very valuable - it depends on your target audience.
For example on mobile, connection speeds in major cities in developed countries maybe rocketing, but substantial areas still need to make a lot happen with very little bandwidth. So it can be a small competitive advantage.
See my reply to your sibling comment. You can measure very real changes in SEO, user engagement, bounce rate, conversion rate and sales on even small changes (100ms) in page load times. I have personally seen conversion rates vary by 4x based on page load speed.
For example on mobile, connection speeds in major cities in developed countries maybe rocketing, but substantial areas still need to make a lot happen with very little bandwidth. So it can be a small competitive advantage.