Ancient Tomb was made legal again one year after the format was changed to start with 20 life points for players under the assumption that the card would be kept in check by the lower life total and the viability of aggressive decks. While it is true that this land is somewhat painful versus aggressive decks, it is also a fact, that those precise decks are using the card themselves.
Trading life for resources has always been a dangerous mechanic and it is even more dangerous when being done while being the aggressive deck. Ancient Tomb makes no exception to this and allows for explosive starts. By providing permanent extra mana on the turn it is played, it is a huge tempo gain - especially when it’s used to cast and recast commanders. Whether being used to cast commanders or expensive spells like Damnation, Fiery Confluence or Thought-Knot Seer, the result often easily mitigates the damage done by Ancient Tomb most of the time. In order to keep games more interesting and fair Ancient Tomb has to go.