As another idea, what if the amount of turns required for a tech increased in speed as the eras progressed? That way, you could dramatically speed up research in the last couple eras to reflect the recent tech boom.
Certainly possible, I prefer keeping it at a constant rate for simplicity for new players.
Do you get a popup every 8 turns „please chose between X and Y“ or how do you set a path as a player?
I imagine being able to view a tech tree and set a path or if no path is set, getting a popup when it's your turn to chose a new tech.
And if I then go deep, will „the Wheel“ cost me the same as „Feudalism“? Because that sounds counterintuitive.
Based on the core idea, technically the answer is yes the wheel and feudalism could cost the same (in a time sense, if both are available at the same point).
I‘d rather favour a system that puts more emphasis on the actions of the player, kinda like the Eurekas, but more so. If you do X, the chance to research Y increases.
Maybe combine that with your idea and instead of chosing the tech after 6 turns, a probability will grant you a tech. Those probabilites are transparent and you can manipulate them. Lots of Horsemen and Farms? Feudalism more likely! Another Empire you trade with has a tech? The likelihood increases. That would make Great Scientist worth more since they‘d let you chose and allow for beelining which would otherwise be very difficult in that system.
You can make it more active but you have to design the tech tree itself in a specific way. It might be getting away from the basic general idea but if I was designing the tech tree I'd be doing something like (Again, NUMBERS FOR PROOF OF CONCEPT)
Each era there are 16 technologies available
To progress to the next era you only need 8 technologies
After the ancient era, technologies will require an in-game action to be unlocked
Districts/Buildings/Units etc unlock based on when you progress to a new era (Not specifically linked to an individual technology)
Technologies instead boost aspects of your empire, rather than unlock stuff
For example you are playing a game, you are doing lots of fighting with swordsmen. That allows you to research Bronze Working, which boosts Classical era melee units by +4 combat strength. You are going straight warfare, so next you research Iron Working, then Iron Smelting, each giving you an extra +4 combat strength, so now you have +12 combat swordsmen.
Someone else builds a commercial hub, unlocks barter, then trade, then coinage. Each of their technologies creates a trader and trade route to be completed one time, before the trader "expires" (So to not give a lasting whole game benefit).
Again this is more tech tree design though rather than progression, even if the two concepts are related.