Exactly, and it's fine that he prefers V, but he is pretending that V is objectively better and you can't deny it.
I'll get to your larger post when I have more time, but the issue I'm most interested in is not Civ IV vs. Civ V, which has been done to death by me and others, but the 'why isn't Civ VI closer to Civ IV than Civ V?'.
And this is my answer: from a mechanical standpoint, Civ IV was a clunky, obsolete design - it was a great game that got absolutely the best it could out of those mechanics, but if you were to design a Civ IV successor from scratch rather than be beholden to systems developed over the prior 15 years, you would not use the Civilization IV mechanics.
There is no objective basis for good game design, period, and of story. As you (gorbles) are frequently at pains to point out when people criticize BE, presumably your favorite iteration of the series.
I don't treat appealing to a forum poster's opinion as authority, and this doesn't seem a sensible comment without any kind of qualification. Games are designed with specific objectives, and there are ways to meet those objectives that are simply better than others.
Take again the expansion example. You can have a game that tells you 'to win, you must expand' and which adds a mechanic which tells you 'to expand, you must be punished'. What's the focus of that game? If it's to promote strategic play, this is quite simply poor design - it offers only one strategic option and provides penalties for pursuing it.
Then you have the alternative of a game that tells you "to win, you can either expand or you can focus on owning less territory and developing what you have" and which tells you 'to expand, you must be punished'. This offers a choice, at least in principle. In practice it is obviously incomplete, because it presents two strategic options but punishes only one of them (which is not quite true of Civ V, as there are costs to going tall in forgoing the advantages in production capacity and resource access that going wide allows, but is broadly accurate).
Now the above is deliberately generic to get away from the emotive comparisons people insist on drawing between one game and the other, and if someone who didn't know which game each description referred to were to look at these two alternatives, which do you suppose they would consider the better of the two designs?
You note in the other post that the second characterisation is a euphemism for going tall being the only viable option. That's not altogether true - going wide is viable in Civ V and it can be powerful, it's just a lot more difficult and a lot more dependent on the map (as you have to commit too early to know whether it's a good decision) than going tall.
But assuming for the sake of argument that your point is generally correct, that's an issue with implementation, not with the core game design - going tall vs. going wide just isn't well-balanced. Indeed, prior to the patch that nerfed Liberty Civ V was characterised as ICS all the way - all the people who now revere Sulla's review as though it were pertinent to a version of the game 6 years on from release conveniently ignore that one of his key criticisms of the game was that it wasn't as good as Civ IV at punishing ICS. Evidently that would not have been possible if the core game design was hostile to going wide. Which comes back precisely to my point in an earlier post that Civ IV had a worse design than Civ V but implemented its systems better.