^I quite agree with that. There's something annoying in most Civs with music. If I'm correct, in Civ6 they often play the music of the other civs that are in the game too, and I feel it's completely un-immerging. Hearing modern Australia or America themes when you are an antiquity civ has something wrong.
I don't remember how the musics were in Civ4 (except the splendid Baba Yetu of course !), does that mean there was nothing wrong with them ?
I remember the modern Civ3 theme, it was getting of my nerves because very heady, but now i feel it as kinda amusing. (same with Civ2 war theme, now that was a thing - I want it back ! Unless I install Civ2 again)
Best Civ music experience is Civ2 and Civ3. (although I struggle to get the themed music in 2, even with ISOs) (it's like the old good rip I got from a school friend, no music ingame except war one)
I loved also the little intermede music of Civ2, at the very beginning of each game, when you had a picture of Earth as an introduction, I can still sing it occasionnally. To me that music depicts perfectly what is Civ, or at least, what it should be. Early eras are the standard of Civ IMHO. The game should make you feel you go from prehistoric ages to future without transition.
There's a lot to discover for Civ series musicians. They can invent Zulu modern music, and ancient civs in general, in a way you feel you still play the zulus, even in 2049 AD. I don't like too much folklore musics because they feel too cliché and put me out of the game completely.
As I already said, players and devs are focusing too much on strategy detrimentally to immersion. Difficulty levels are here if I feel I have gone around the game at a lower DL than Deity, it's true especially with a game with no uniques like Civ1 or Civ2. That may be a wrong feeling, as there are plenty stories to live not taking into account the difficulty level. But it's not obvious anymore. Particularly in Civ6, I don't feel there is cool stories to tell. Even Civ5 was better, especially in regard of City-States that could become a major focus of a given game. (I mean, 1 or 2 city-states) In Civ2 that was blattant : every game was unique. (last try I started alone in huge continent : I think it should still be possible with modern Civs, that focus too much on balance - not much space to develop, early aggressions, etc.- Don't get me wrong, on paper it's exciting but on practice it's disappointing, because you feel cramped with all those impassable or bad terrains. Deserts and toundra in Civ6 are awful, mountains too, not speaking about the absence of fresh water or a peak to build an aqueduct, that are only one tile range unlike Civ4. This is silly. As you see, a lot of frustration. When I look at Marbozir (YouTuber) playing some games, I feel really crappy for him, I wonder how he do to not shout in despair. In my head I say myself : "hey it's Civ6, what did you expect ?")
So, as it seems impossible to marry strategy and immersion, let's go back to immersion shall we ? Creating great stories, and I'm sure the music helps greatly. I don't mean hurt-heady modern themes, they are a humour of repetition to me, as long as they are completely original. I hate above all when Civ takes known classical musics. I even feel native early music that are realistic are not so good - the research and precision for it asks more work than the actual execution - and for what ? Earing other civs musics ? Nah. If we are to keep uniques, the musicians should INSPIRE from each native culture (no more modern folklore in antiquity) and go with free interpretation, provided the result is cocooning enough. Yeah, that's flavor. Aren't the musics flavor ? I want to feel good listening to those musics. Most of them at least. As I said I'm not against a heady and short war theme that turns in circles, as long as it's well done.
Yeah, music is VERY important in Civ IMHO. Developers do not need to do experiences with music (all failed so far at least since Civ5), they just have to do the things right.