I also started having fun right away. The reason people say it starts slow is that the game doesn't expose you to every aspect of play right away, for reasons both good (it would be a lot to take in) and bad (the game has some sort of allergy to showing you its cool systems and seems to expect you to learn them from wikis instead). So, when people tell me they're not having a good time, I often check that they got to these systems in the main quest before haring off to do side quests without realizing they hadn't encountered key features.

This is a flaw in the game, but the flaw isn't "the game is boring", it's "the game lacks an adequate tutorial". It's still not for everyone but a lot of the people I talked to were pretty happy once they learned they were missing bits.