What was so enjoyable about it before the change? Personally for me, it was always the roulette I got the least amount of enjoyment from WHEN I actually decided to queue up for them. There was nothing enjoyable about Castrum/Prae for me, ever. It was a zergfest where no one gives a shit about anybody. People say they like to help newbies through these instances, and I have never seen that. Not even once. They get left behind. Always. Being carried though an instance isn't the same thing as helping, and that is exactly what was happening to the sprouts when they get to this point in the story.
I have now queued for both Castrum and Prae everyday since the patch. The environment is far from being filled with a bunch of people pissed off about the change. I'm not saying everyone is all happy about it, but there is actually social interaction going on in here now. Yes, players are actually talking to each other to pass the time while those who want to watch to cutscenes will simply just watch them. Hell, one player was having trouble figuring out how to get into the magitek mount, and one went back to help while the others actually waited. I can't even begin to express how shocked I was. This player was so happy when he got to join the magitek onslaught portion of the dungeon (seriously one of the more fun parts of it).
In short, I have seen far more good come out of these instances in one short week than I ever have in two years playing this game. These sprouts now won't know the horror most of us have experienced, which is far worse than oh soo torturous 90 minutes the veterans are having to deal with. And from my experience this week, veterans having a horrible time here would be an inaccurate assessment.
Don't get me wrong, I am not saying the way they handled Castrum/Prae was the best way to do it. However it is great to see the community come together to make the best out of really long instance time, which never would've happened without this change.