Why Did Lodestone Golem Get Restricted?
Here is the official statement from Wizard's of the Coast:
"We continue to see an imbalanced metagame. In particular, Mishra's Workshop–based decks continue to be significantly overrepresented, reducing the competitive metagame. While this issue could be solved by restricting the namesake card, if possible we would like to keep the deck at a competitive level, but played to an extent that the format is more diverse overall. Lodestone Golem leads to some of the less-interactive games. We are hopeful that limiting Workshop decks to one copy of the card leaves the deck at an appropriate strength. For that reason, Lodestone Golem is restricted."