Knowing developers never corrected what I see as a major bug (the workers being asked every_turn for what to do in previously endangered zones but not anymore), I see it as they considered everyone switched to expansions. (the bug is not over there anymore) And they are nearly true, actually I'm quite happy to see you talking about vanilla, because that's the version I currently play too. So we are 2 now.
If I don't buy the expansions, that's because
1) I never quite catch a sale on them (and without it they are quite expensive still)
2) I like more wonders (Petra, dear Petra), but I like also less currencies (religion, bah

, tourism, meh) and the ability to push culture further than just +1 per costly building. (not to mention happiness buildings that are more rewarding) The downside being that maybe cultural, space, diplomatic victory are all obtainable quite rapidly all three only at the end of the tech tree.