I didn't get all the way to the end since my save has already reset multiple times after accidentally clicking anything that refreshes the page, and loading my save did nothing except make the whole game unplayable, but here's my final rating:
Fun: Not very fun. Game is very slow and doesn't speed up with more prestiges. You also don't know when the next prestige is gonna show up, which is a problem especially when it's such an integral part of the game, and creates a sense of confusion. Getting eras doesn't really feel like you're progressing because the only thing that changes is the name. Regardless, the game has done an okay job of making all the buildings stay prevalent.
Uniqueness: I like the premise of eras as a sort of prestige/level mechanic. I would give it higher if eras did more than unlock new upgrades (Which were already shown to you anyway). There was time now also features a similar system where "eras" unlocked new resources but unfortunately they felt too independent. Maybe a system where eras unlock new resources and sciences which give boosts to production.
Theme: Again. The only real prevalence to time is the eras mechanic and the names of the buildings (which don't really affect production).
Additional feedback:
Display for net currency gain/gold gain per sec would be nice, along with a display that says reach <x> gold (or is it currency? I have no idea) to reach the next era. Hide the upgrades before you reach them so there's a real sense of progression through each era.
Add displays so that people know what a "human" and a "machine" is.