Thats also not to say that I think Autumn's Veil or a similar card doesnt have a place in a 75% deck, because thats not true
While this card is capable of dealing with dangerous threats, you can also use it to deal with massive token-based boards, granting the card even more flexibility
Whether Mephidross Slime should see play would depend on the overall strategy and synergy within the deck, as well as the current metagame and matchups it is likely to face
Some matchups are going to bring in lots of cards to specifically attack your enchantments, so having quality threats that are good on their own is important
thats because each one is printed in the language that the actual historical figure spoke
This time, you can recur, for free, an artifact from your graveyard to the battlefield