Bringing the right weapon
Which kind of fight do you want to fight?
This doesn't eliminate white from the format though. White has always been known for its wide arsenal of hate bears and it has one of the best trumps for creature brawls.
Stoneforge Mystic allows you to bring an arsenal of swords to a fist fight, which usually is enough to win those battles. The problem is that there is also the other part of the Legacy format – the combo decks which don't have to fear Counterbalance anymore. Bringing swords to a brawl might be great, but bringing them to a gun fight will make you look pathetic. Therefore, the creature decks need to able to disrupt the combo decks somehow. Obviously, there are various tools to do so, and due to Cabal Therapy it also makes sense to diversify your disruptive options, but many of them are white as well, so they fit into the Stoneforge Mystic decks. Containment Priest has unsurprisingly been on an upward trend due to potentially preventing both Reanimator and Sneak Show from working their Magic.
The other white creature you really should own by now is Ethersworn Canonist though. It wrecks Storm, but is also very annoying for every other deck interested in doing multiple things per turn, whether it is casting lots of Elves or chaining cantrips. Sales numbers have continuously increased in recent weeks, rising from single digit sales up to between 20 to 40 per day. With only 300 copies from Shards of Alara and less than hundred Modern Masters copies remaining on MKM this activity could soon cause the price to spike. There are other signs for a price correction as well. On the other side of the pond SCG has run out of stock on both versions of Ethersworn Canonist and the respective foils as well. They sold out while their price was $9.99, so they will most likely relist future copies at an even higher price. Therefore, picking up Canonists at their current rates on MKM sounds like a good idea. The card doesn't seem iconic enough to be reprinted in Iconic Masters, so its price should be able to continue upwards for some time.
Ethersworn Canonist From (EX+): 2,50 € Price Trend: 4,08 €
Obviously the card is Modern legal, so it can be used against Combo decks there as well.