The specific third space everyone longs for as an adult is the cafeteria. You all just miss the cafeteria. You miss going to the dining hall and the whole community of people you know are there. You want to be able to go somewhere and be around friends without explicitly having to make plans to hang out.
I feel like Discord servers can occupy this void in some small manner. Passively able to interact with large quantities of people without needing to specifically seek individuals out