Citadel is a dead end.
Good for what it attempted to be. Warm moments with characters are always nice. But no amount of that, no amount of 'fun character time' is going to solve what went wrong for ME 3. Citadel is not the path to good plots, good characters, and good style.
If you want to hide away in your 'happy fun time' DLC, so you don't have you think about the very real and real immense difficulties in writing a strong story, go ahead. Thankfully for you, there are people like me willing to do it for you.
But don't pretend there isn't real work that needs to be done and real problems to be solved by real thinking. Citadel is nice. I enjoyed it. But it isn't the answer to anything.