Golos was banned for a few reasons: hoping to diversify Commanders for five-color decks, his ability reduces the Commander tax, and it allows you to constantly play free spells. Being able to slot Golos into almost any deck at little cost stymied diversity as the Tireless Pilgrim has been the most popular Commander for years. Golos was deemed unhealthy for the format and the article recommends Kenrith, the Returned King as new five-color good stuff deck Commander.
Other news in the quarterly update was the unbanning of Worldfire.
The Commander Rules Committee wants to foster a community where eight and nine-mana spells are viable. It was previously banned due to the ability float mana and have access to your Commander. The RC said it is safe to unban as it isn’t a cheap “win the game” card like Coalition Victory of Biorhythm.
Lastly, Rule 10 was removed due to its redundancy. The rule stated, “Commanders are subject to the Legend rule; a player cannot control more than one legend with the same name.” As members of the RC couldn’t remember off hand what Rule 10 was, it was removed.
Read Sheldon Menery’s article breaking down all the decisions from Star City Games.