Let me play a little devil's advocate as to why maybe OP has a problem with paying for new content.
I can recall a time (and maybe so can OP) when the DLC wasn't a thing, and if a company want to add content to a PC game, then they had to come out with a expansion pack, which tended to be fairly meaty in terms of content compared to the little bits and pieces we as consumers sometimes get with DLC content.
Another sticking point is the base game itself that you alluded to. Some people would argue that the base game would be even deeper (yet not more expensive) if there wasn't this temptation to maybe "hold back" content for later in this modern era of gaming, where it so easy to distribute content online.
Now, I don't begrudge game companies trying to make money off us, but gamers shouldn't begrudge other gamers who want maximum value for their dollar, and therefore have issues with DLC. You may not agree, but it is certainly not a silly thing to get upset about from some people's perspectives.
I understand these reasons in other games, but they don't really seem to apply to Civ in my opinion.
I don't think the game is really "stripped" of content, because like somebody showed above, the number of Civs in the base game remains consistent. Even more so, Civ 5 and 6 have both gone additional steps to make each Civ have somewhat unique gameplay, so in terms of overall value, the games have increased the package they have to offer. Some people make the argument that "If they didn't sell these Civs as DLC they would have been in the base game!", but... no, I can't follow that logic. The base number of Civs has obviously been accepted as a decent amount of Civs, so if those small-scale DLCs didn't exist, then those extra Civs would probably just not exist at all, because why would you increase the number of Civs, and thus not only increase the work you have to do, but also increase the expectations for each future iteration of the game, when people are fine with with the way it is?
About DLC... well, Firaxis still creates expansion packs for Civ, and they don't really seem to suffer in content. The way I see it, those "small-scale"-dlcs are mostly a filler for the time where the Expansion pack isn't in production yet. You can't really skip that initial "waiting" phase, because before you can get into starting to code stuff, and starting to create assets, you have to gather data about what people think is missing the game, build a general idea of what you want the Expansion to be. That's exactly the spot that the small-scale DLCs fill, they don't require too much groundwork and keep the programmers and designers busy, so I see it as mostly "extra content" that wouldn't have existed otherwise.
People who don't have that content don't really miss that much (although the way mods are implemented is a bit problematic, often times mods require certain dlc-packs), because it's just content "on top of what already exists", the core gameplay stays the same. So if money is an issue, people can just wait a few years and then get all of the small dlc-packs in a big sale. This means that in the end they still get more content than they otherwise would have.
