It's a very deep game but doesn't have to be overwhelming. I've been playing the various iterations since the 90's and still love it. But I will say I rarely finish a game, I really love the exploration and early historic periods like building ancient wonders and just play casually for fun with randomly generated maps. Once you get into the Industrial or Modern era and your pumping out tanks and such I start to lose interest but that's just me.
One thing about Civ 6 though is the base game has some very frustrating aspects to the AI. One in particular is that they are big land grabbers which ticks me off to no end. I will have a nice area explored with good resources and something strategic that is a perfect fit between my capital and another city. While building my settler 9 times out of 10 the AI will plop a city down there before I can stop them even if their next closest city is half a continent away. The expansions fixed this thankfully and added some fun features like volcano's and floods, some new civilizations to play, etc. They should be sufficiently cheap to easily purchase now. They do add a lot more features though, so could be a little overwhelming to a brand new player.
