The January 13th Banned and Restricted list announcement removed three cards from Modern:
Oko has been seeing more and more play in Modern, with blue-green based Urza, Lord High Artificer decks using the Planeswalker and Mox Opal to great efficacy. These decks have maintained a non-mirror win-rate better than 55% on Magic Online. Oko has also cropped up in several other decks and removing him from the format should allow for an increase in diversity. In order to curtail Urza decks without completely hampering them, Mox Opal has also been banned to cut off explosive starts.
Mycosynth Lattice is part of a hard lock with Karn, the Great Creator in various Tron decks. Cited as an “unfun play pattern”, Lattice got the axe to weaken various Tron archetypes.
These bans go into effect on January 14th, 2020. The next Banned and Restricted List update will take place in approximately six weeks time.