Average playtime without side quests I’ve seen about 60 hours. I’m at 40, there’s 8 characters, and I’ve only been focusing on 4 of them. My playtime may be off, though, because there were a few times I left it paused for a few hours.
If you like old school, but new, games I have to recommend Octopath Traveller 2. I started it 3 days ago and already have 30 hours with no signs of slowing down.