Conferences aren't always a great use of our time, but it allowed us a social escape valve, and it seems to me that just isn't the case anymore. 10 years ago, you'd go to a conference and there would be a massive group conversation about it on Twitter. Not just sessions, but people wanting to get together, eat, drink, and be merry. A simple hashtag search pretty much gave you a quick avenue to meet new people. Now that's pretty much dead, probably due to how people use Twitter and social media, but also the backlash toward it and its owner. Nothing has really replaced that, and most potential replacements either lack the network effects or are essentially restricted in access (requiring a signup or invite).
You're right - Twitter used to generate FOMO amongst those not attending, plus make it easier for attendees to coordinate after-hours events. Both of those factors are diminished.
Twitter used to be a huge conference backchannel. But, as far as I can tell, that's largely gone and neither Mastodon nor Bluesky have really recreated the Twitter of old. I have accounts on all three and I barely look at them and many others I know are the same.
