Cards in mint condition, with no signs of wear or damage, are more valuable
Fifth Edition rules changed how spells and mana worked, allowing players to declare spells, then pay any associated costs
And even though the card has dropped in value with the reprint, demand will eventually outstrip supply due to Commanders popularity, where you can expect the Magic Foundations printing to settle at a similar to price that were currently seeing with the Wilds of Eldraine: Enchanting Tales printing of Doubling Season
Even amongst some of the most respected collectors there are disagreements about what a misprint should be called
If a board wipe is cast in the meantime, whatever creature you exiled is still protected
Before this set we had 40 cards that could Proliferate, now there will be 74