The raid should have been great. There are great characters there, a great background story. Everyone wanted something with new rewards to go after.
Then the raid debuts, and it's so ridiculously difficult that it's no fun. (not difficult in terms of complexity, as someone said above, just artificial difficulty - even when you're doing it right it's nigh-impossible).
Then there's a very significant nerf almost immediately to a 'strategy' which apparently nobody noticed in testing.
Then we find out that the rewards suck. Just plain suck, for the amount of effort and the power of the characters needed to succeed in it. I mean, obviously there's a problem with the rewards if guilds are just autoing it at T3 because nobody wants to slog through the fights for what you're getting in return.
Apart from these, the gameplay in the raid is just not fun. Like someone said, it's not all terrible, but Nihilus in particular, you just stand there and get beat down. The guild zergs him to death. Yawn.
Sorry to be negative, but many of us have invested a lot of time, if not money, over the last couple of years, in SWGOH. It's disappointing to see so much effort to cravenly monetize new content (i.e. the vet smugglers) vs. deliver compelling content that will cause people to want to keep playing and generate revenue for them in a net-positive way.