It looks like they are going to be releasing every evolving building one by one into the spire. This doesn't make it better. I think it's a horrible idea. As
@Gargon667 says, it makes sense for them to do it with 2019 Phoenixes. They are powerful enough that everyone needs to have them, plus also there was a choice of three so most people did not evolve all three the first time. There would also be a good case for doing the bears, for a similar reason. Releasing all these other artefacts as spire rewards is just depressing for any player who was here the first time. Even for the newer players it's not that exciting because they're not amazing buildings to obtain like the Phoenixes.
As far as we understand it, the Spire Library pieces will only be made available to craft if you don't already have at least one of a given piece either in your city or your inventory.
I do not think it's a horrible idea, I am pretty sure most people play the spire for all it has to offer, not just the moonstone set.
I am fine with the moonstone set going into the academy tho that creates other "minor" issues, but issues none the less.
There are a lot of players who are new to the game, and how many times do we have seen the complaint if I can't get the artefacts so why offer the base? in fact this is why those bases got removed from the academy.
This change is great for new players, and good for innogames.
Innogames gets an easy way to recycle a lot of material they already invested money in. so it's cheap. and new players get a vast array of new possibilities and enticements for them to play the spire.
They see a base in the academy, figure out the need artefacts and then end up in the spire.
These "useless" buildings might be useless for us. the veteran players who have seen and got it all in the past and have seen better, but we have to look broader outside of own personal horizon. and for that this seems to be a good move non vetaran players havent seen it all and havent got it all. this is there entry to it.
For us vetarans in outr veteran world there is plenty other stuff left in the spire to enjoy. we are already there. we don't need an artefact to lure us there and we will keep playing it anyway since those artefacts are not our main goal and reason we play it anyway.