Yeah, you really need to get a dedicated group of people who are willing to play and commit to the time. Also, we only play TI on weekends. We usually start around 12 or 1pm and finish around 6 or 7. I would never play TI on a weeknight.
Other than Pandemic Legacy, which doesn’t really count because it’s a campaign, Twilight Imperium is probably the closest I’ve ever come to a transcendent experience when it comes to boardgames. With the possible exception of Twilight Struggle, I have never played a game as strategically and tactically deep as TI, that also manages to be incredibly thematic and tells a compelling story.
You might not think so, it might not be the game for you, but unless you’ve played TI, you won’t understand what it’s like to play it. Without wanting to go too deep into hyperbole, Twilight Imperium is more than just a game, it’s an experience.