While Twitter has absolutely degraded in quality over the past year or so, it is one of the last places were experts still interact with people.

I remember in the early days of Reddit it was pretty common to interact with all sorts of relatively well known people in their field. Now it's just soccer moms and bot farms.

While there are still a few experts lurking around HN, I've noticed this has declined as well over time. In part I suspect because the HN crowd has increasingly become surprisingly less technically expert on average.