EQ was made with a budget of 3.50, and places like Lower Guk were FULL of players, like literally a full group in every room and some corridors too. And yet, we made do. There were occasions when it wasn't too great, but I found other places to go. I went to Sol B and that was full, so I went to kedge and realised I couldn't solo there and couldn't get anyone else to join me. But seeing as I was already on faydwer and desperate to kill something, I explored, and found steamfont... The little stupid gnome guards wandering around acting tough. So I killed them and got a shit ton of exp. And nobody ever went there, so I had the whole place to myself, got several levels there alone.
Some of my guildies and buddies just started another character and ended up preferring it to their main guy, so they no longer gave a shit about lower guk because they were back in Cazic saying, "I forgot how fun this place was!"
People made do, and again, even though it was a very small game and small budget. Nowadays with a bigger budget, I am sure people could make do even better.
But I am sure they will use instances somewhere anyway.