Many will disagree with you. Yes, the mechanics are good(That is, the gunplay, the movement, the things where a player has agency).
However...beyond that. The looting system is awful. Legendary Engrams rarely give Legendary things. Having to grind factions, reputations, currencies? That's WoW level of dedication right there(Even then, it speaks that Blizzard is removing Valor/Conquest/etc. Next expansion). Having separate Crucible Marks and Vanguard marks, yet the majority of items requiring Crucible Marks to obtain, and on top of that imposing a limit of how many you can earn a week? Bungie says it's not an MMO yet treats it like an MMO.
Then there's the fact that so far it seems faster to grind PvP in order to get exotics/Legendaries than it is PvE, there is a huge dissonance in that. Why is PvE not giving out rewards that are worth doing PvE? If you're interested in the looting aspect of it, then it looks like PvP is the fastest way to get what you want(Yesterday I was in a group with friends, and someone in my party earned about 4 legendary engrams within a 45 minute span. In Comparison, I've ran the Vanguard Strike list for about 3 hours and only earned 1 Legendary Engram in the same time. Anecdote, but I'm sure I'm not alone.).
So yes, the gunplay is good. The lore? Fantastic. The art style? Solid foundation. Everything else? It can use work. Would I call it a good game? I'd call it enjoyable. But then again, I enjoy Dynasty Warriors immensely, that says of me that I enjoy the repetitive nature of games. But that also means it's just as easy to see the flaws in something.