It wasn't at first. It launched as a pretty buggy and featureless game. The devs have worked very hard with it over the last year or so to add new content and kickstart the playerbase.
I don't remember it being that buggy at launch, I played a fair bit and never had any major issues. I agree they have kept adding to the game but I think it was fairly popular out the gate with a certain type of playerbase. A lot of people went into the game expecting it to be a lot more structured and it wasn't that which fed into the narrative of it being a failure but the base game had a lot going for it if you were into the game space it created.
Lines up with Gold yearly subscriptions going away and perhaps explains the Halo Infinite retail listing that appeared on Smyths saying multiplayer would be free.
Great move in my opinion and really puts Sony in a corner especially as PSPlus has looked worse as a value proposition for a while as they have slowly removed stuff from it.