That's fair. And yes, it's always disappointing when you're near the end and the most recent era is one that's not "your flavor" - I think during SAAB was when my highest era city got converted to a diamond mine - not all SAAB's fault, but it probably contributed some that I really didn't like it.
Sometimes I mind those eras less when i'm not stuck there. i.e. I was very unhappy in OF when it was the last era (no GBG at the time, so that wasn't even a consideration - but I was wishing to be back in AF - at least in part because the hover tank was even stronger in OF than in AF and there was a lack of challenges at the time to try and motivate me to using other armies so GE4 was simply the "hover tank shuffle" which was easy, repetitive, and tedious). But on my "new main" when it passed through OF I actually enjoyed my time there.
One thing I learned though from playing the "should I move up?" game with other players experiences in my first world is that it's highly unreliable. People told me to move to FE from TE and I hated it and wished I'd stayed in TE. People told me not to move to AF, and I ended up loving it when I eventually did.
When OF came out I was finally at the end and was no longer asking the question anymore - not that I would've trusted the response I got from others anymore. I've moved up at release (and either regretted it or loved it) for every era since on that original world of mine.
Currently my new main is in VF, and was already planning to move to mars. I'm now making plans to run it to Titan fast because of the GBs, but the SAJM diamond mine will move up first just to be sure it's not intolerable. But even if it is, it's in the long run just another flavor to pass through