After having heard the podcast, some new thoughts and reflections. Moo1/2 and Master of Magic had what I call hybrid mechanics. Combinations of strategy with tactics, with layers of gameplay to create a richer gameflow. Things get stale if you do A B C in the same order. At the time, their A B and C were pretty new, each in their own particular genres. For example, people have had turn based strategy games, they called them war games, back then as well, perhaps even on the PC. But they didn't have a mechanic where it simulated the tactical layers. The Total War series was notable for that reason as well. A lot of notable games early on, were using the superior hardware specs of the time to combine and hybridize different genres of games. Instead of specializing in one type of gameplay, they tried mix and matching, to see what worked. And some worked better than others as a result.
The modern 4x games increase the scaling, but they don't increase the complexity of the interlocking gameplay mechanics. In fact, Endless Space doesn't have an interesting card or turn based tactics game. An interesting "tactical" layer is what Total War series has, what SOTS1 has, what card battle games have. That's an entire "genre" of game mechanics all on their own, including Xcom's turn based squad tactics game. So when the new Firaxis Xcom 1 came out and the Xcom 2 came out, they kept to the core squad tactics game and made it great, with some minor changes to the strategic layer, until 2 where the strategic layer changed much more.
What people back then had was stuff that worked, and they just hybridized the systems. Whereas the newer 4x es were replicating a formula, cloning a combination of systems, without necessarily having a single rich system to center around.
The key to Rome 2 Total War, was the tactical battles, and when they broke the AI and other stuff on release, their core shattered as a result. Plus some other stuff people complained about. The key to SOTS1 was the real time with pause tactical battles, under a simplified and easy to use strategic UI and gameplay flow. They broke that in SOTS2, by overcomplicating the UI and strategy, which also caused more bugs, more barriers to enjoying the tactical fights, and more UI ease of life problems.
The key concept or gameplay that Endless Space was around, was basically a watered down archetypical formula, 4x. Which was merely a marketing label and not so much a design vision on how to combine different elements of gameplay together. Endless Legend brought out the quests, rpg stuff, and customizable army units, and things got generally more interesting as a result. It was able to bring out a lot more of the flavor that Master of Magic and Civ series had. Going through FTL lanes and colonizing planets, isn't a hybrid gameplay or genre. It perhaps, never was.
There are entire games with relatively good renown, based off one gameplay and gameflow. FTL, Don't Starve, other rogue likes etc. Old xcom essentially had each tactical mission be like that flow, with a set beginning and end. Except combined with a strategic campaign, so you could save your progress and goodies with some rpg stats.
To be capable of creating a hybrid game experience like MoM or Moo1, people needed to have a strong foundation in a single gameplay type first. And then gradually add hybrid layers to them. For old games like Moo or Xcom, generally people don't like radical changes, so the first game has to be "conservative" in order to prove the bonafides of the company designers. The next one after that, can become more radical. But only because the designers have proven that they understand how to create a rich/deep fulfilling gameplay that is of one type. Even if that type seems a bit shallower from Firaxis Xcom to old Xcom.