Regarding constellation, there was a entire deck in that standard format where enchantment lands would've broken it by providing insane card draw and actually endless wrath effects on the back of Eidolon of Blossoms and Doomwake Giant.

An enchantment land would have caused problems.

"our experience with artifact lands... would have forced development to raise the costs of all the cards with the constellation mechanic." Yeah but constellation triggers on enchantments played after, not counts the total including those played prior to the card like affinity. So enchant land played on turns 1-4 doesn't do anything broken. Drawing 1 extra off Eidolon of Blossoms turn 5 is meh. Especially since Nyx could have been legendary land, so it only happens once.

Despite your disbelief, an enchantment land would very much power up constellation.

I liked that it seemed Enchantresses had moved into white, as white likes enchantments the most, but the awesome Eidolon of Blossoms shows that greens history with them still strongly affects present day Enchantress design. So are they still mostly a white thing, or is it back to green again? Also good call on Constellation I can't wait to see more white cards with it.

The “Enchantress” ability is both green and white.

Why isn't Eidolon of Blossoms blue? Creating enchantments = growth?

Enchantresses, green creature that draw you cards when you play enchantments, go all the way back to Alpha with Verduran Enchantress.