neodymus wrote:

1) Trigger era progression possibility upon researching 1-3 era-end techs (similar to endless game requirements). If worried about science cultures racing ahead, maybe allow claiming a culture after 7 or whatever era stars, similar to claiming wonders with influence.

This would force everyone to focus on science and turn the game mostly into a science race.

neodymus wrote:

2) Make era progression static. I get that it feels cool to have dynamic era and culture progressions, but if you want to target 300 rounds as end of game anyway, then just allow the same amount of turns for each era and force progression (with possibility of ascension) after reaching the specified turn. Use the amount of era stars gathered for priority on the culture pick. E.g. each player to pick new culture at same turn, but if I got most stars, I got first pick on it.

This could make players that focus on science get stuck at the end of an era with their research until a certain point in time has been reached.

Also decoupling fame from the eras seem difficult to do (and probably lead to a bunch of exploits) with the current version as fame stars reset on the era change.
Personally I also like that with the fame system it is possible to advance to the next era in different ways. I have faith in the developers to get the pacing to a good place by changing the speed of era progress, research, construction and AI priority to go to the next era. However, I do agree that in the current version the pace of the game feels far off and by looking into general feedback here this seems to be a common opinion.

I like playing on slowest setting (Marathon in Civs, Endless in... well, Endless) and I'm super-afraid of this, because I imagine there will be (as it unfortunately tends to be) little thought put into balancing the game for such settings.

I could see an attempt to make the possibility to go to next era be locked behind scientifically putting your foot in the door, i.e. researching one of the top techs for the era, but, imo, it's too late to test that. That's something that could be done after Lucy to test in Victor. Currently best we can hope for is that the devs will tweak it further, I feel like it's in a slightly better place currently than it was in Victor. I just doubt they'll be able to hit anywhere near a perfect spot before release.

I think the current system is fine, maybe era stars are too easy to get but basing era progression directly on science instead of indirectly like now is a bad idea and go against the system. The current system allow for some cultures to be good when you are behind in technology such as zulu.

I feel like progressing through the era's feels a bit too passive. Like you said the era stars feel a bit too generic and during my first playthrough it often felt like "Oh hey I have enough stars guess I will go to the next era". Which is kinda sad for how much work is put into the era's, and different cultures.
Personally, I would love to see a bit more flavour associated with progressing to the next era and specifically about that transition. I feel like my suggestion flows into yours nicely.
What I would suggest but is a lot of extra work is the following. After unlocking a couple of (generic) stars you get a quest or series of events either specif to your culture, the mix of cultures you have chosen (I know unfeasible but a man can dream) or your culture type. Something like you are given 5 objectives of which you need to complete 3. So for the classical era that could be. Have discovered writing, Have a city of 10 people, Own a horse or iron, resource. Traded with another player. After completing one you get a bit of flavour text or a cutscene (again a man can dream). How I think this will help the problem you are describing is that you can streamline the quest more easily. You can determine a couple of requirements you know people need to meet to progress and balance the pace a bit more around those will still giving the players the freedom to progress the way that most suits them

The point is that one doesn't have to specifically focus on one thing to be able to advance. Science based advancement gives to much weight to science, and goes against the theme of advancement being more cultural than technological.

You're unto something because I also think the design choices for Fame and era advancement doesn't really work.
I personally don't like the fame mechanic in general; I get that it's made to give the players some sort of freedom to do a diversity of things throughout the playthrough without necessarily having to lock yourself into a single strategy. However, i feel like it makes the whole experience a bit dull. Perhaps its a personal thing but I don't get particularly excited just collecting points to see If i can win the game. I much rather have a few possible dynamic  but rigid goals that I can aim for.