I'm actually curious how I would have reacted to crises and age resets 30 years ago. I remember very well when I first played civ 3 (after playing a bit of 1 and a lot of 2) and I was crushed in every game. I was so attuned to playing through the earlier games with ease (probably on settler, but I don't remember), taking some cities when I wanted, but being hardly bothered by downfall or enemies (except barbarians). It took my quite a while to learn that the experience of civ 3 is completely different (for me personally) compared to the games before, but I saw it as a nice challenge and was happy to actually learn the game (and the franchise that I already played for years).I also actually believe this could be a viable and even fun game mechanic.
Even if so, though, I would not advise the developers to build a game around it. Here's why.
It could be fun for us civ veterans--to become skilled in both gradually building a snowballing civ and preparing ourselves to best handle a known coming downturn.
But it's not good for hooking new players, I would think. Civ is complex enough, when one first picks it up, that one doesn't need to be told 1/3 of the way through one's first game: "oh, you know how you've been building, building, building? Now, instead start bracing yourself to minimize the number of things that will be taken away.
I think back to my first games. That would feel like too much complexity to me, in a game that I was already struggling to understand. It would feel like the game didn't know what it wanted to be, like it was schizoid. And I'd probably just have walked away from it. The relative simplicity of Build, build, build at least has the advantage of helping with the onboarding of new players.
Edit: I guess I'd add one more thing. There's a kind of player who doesn't so much prefer challenge as just beating up in the AI. People like that would be put off by severe setbacks.
Now, I'm also liking the reset in 7 (which I'm used to from other games), and I wish crises and reset would be stronger or more consequential. There are these games in which I'm looking back and remember the ones where I just blazed through as the peak experience (e.g., most city builders or eco games like anno), but in strategy games, I usually have my peak experiences in games in which I lost stuff, recovered, or barely won on the last meters. Unfortunately (?), playing civ in the past 15 or so years has become more and more of the blazing through instead of struggle to keep your things together. In short, I guess I'm just a bit of a snowflake when it comes to having stuff taken away, as I'm not alienated by it at all.