Unlike base game ME3, this might be some of the best content in the entire trilogy. It's ridiculously goofy and over the top, but also fully aware of it and was just a good fun ride that also shockingly has some fantastic level design that really considers ME3's combat mechanics in mind (far better than the base game does). A far better send-off to these characters and world than the real ending to the game does.
Honestly, the only complaint I have with Citadel is just that I wish there was a better place for it to fit into the base game because there's not really an ideal time in the main plot to start it. It's best played before the last two main story missions because you'll have the entire cast available, but doing so also interrupts the tension and immediacy of what's going on in the main plot at that point too. Not the greatest, but it's also not too big of a deal to me personally because the content alone more than makes up for it.
Honestly, the only complaint I have with Citadel is just that I wish there was a better place for it to fit into the base game because there's not really an ideal time in the main plot to start it. It's best played before the last two main story missions because you'll have the entire cast available, but doing so also interrupts the tension and immediacy of what's going on in the main plot at that point too. Not the greatest, but it's also not too big of a deal to me personally because the content alone more than makes up for it.