alt Hacker NewsMost web devs get screemed at (by their peer reviewers or [preferably] static analysis tools) if they use a feature which has less then like 98% support without gracefully denigrating it, and rightfully so.
But your GP is in a massive minority, if every developer would cater to 11 year old browsers we would be wasting a lot of developer time to inferior designs, with more hacks which brake the web for even more users.
I don't know about "most". For various reasons, I use a 2-year-old browser on a daily basis (alongside an up-to-date browser), and I routinely run into websites that are completely broken on the 2-year-old browser. Unrelated to outdatedness, I recently ran into a local government website that e-mailed me my password in plaintext upon account creation. I have no way of accurately quantifying whether "most" web developers fall into the competent or incompetent bucket, but regardless of which there are more of, there are a significant enough number of incompetent ones.