It is a Great Building from the Arctic Age. Why should there not be at least one GB that is more usefull in higher ages than in lower ages? I think it is high time for such a GB. It means, that may be a better strategic decision to build the vault in later ages, and not early on. There may be GB that are usefull in lower ages, but none - beside the vault - that is more usefull in higher ages than in lower ages. I think to have such a GB in the game is something nice and interesting.
I agree with this and that is coming from someone below ME with a Seed Vault in their live city. Very very few things about this game make aging up appealing or better for the player, in my opinion of course. Having a small silver lining to something improving later on is a good thing.
That being said having used the unofficial wiki before building it I was never expecting it to give more than 10 goods in any era. Did anyone who built it think they were going to get +20 refined goods ME and up? In that way I don't look at is as a nerf since it was giving what it's always said it was going to give and what it said you were going to get when you built it. That's not a nerf, that was an error that had been working in your favor since you put it down.
If I go to the ATM and request $20 and it spits out $40 then next time I go to the ATM, ask for $20 and get $20 the ATM didn't break the second time, it was broken the first. I'm not going to complain to the bank that I'm not getting $40 because I did last time and have come to expect it.
I like the seed vault however neither me nor most people who I've seen have it bother to level it. The real abomination with SV is the lack of percentage gained with each level. It would be a much more popular building if leveling it 1-10 did something useful. It's a shame that some of the new GBs were made ignoring levels 1-10 and expecting people to take it to 80 or not bother at all. Unfortunately it would be my guess that it's too late to change it now, if you increased the percentage of the lower levels without increasing the higher levels it would be unfair to those few who did spend all those points to get it up there.