Being able to hit all creatures without flying and players is fairly useful, especially if you’re running a lot of fliers that won’t be affected by it. While no one in Modern will be playing it soon, Molten Disaster is quite playable in Commander. According to EDHREC, the premier resource on the Commander format, Molten Disaster sees play in 25% or more of the time in 5 Commander decks. They are Diaochan, Artful Beauty, Heartless Hidetsugu, Ashling the Pilgrim, Rosheen the Meanderer, and Chandra, Fire of Kaladesh.
If you haven’t heard of Diaochan, that’s ok - most people haven’t. She was first printed in the extremely rare Portal Three Kingdoms set and was included in the short-run Commander’s Arsenal premium foil set. She has a tap ability that destroys a creature in exchange for letting your opponent choose a creature to destroy. She makes for an interesting political deck. In that deck, Molten Disaster helps you clear the board to make Diaochan’s ability more relevant.
Molten Disaster’s inclusion in Heartless Hidetsugu is more straightforward - it’s another way to help set up Heartless’s tap ability to cut everyone’s life totals in half. You can use it to make sure you’re at an odd-numbered life total so that you don’t fall victim to any damage-doubling effects often run alongside Heartless Hidetsugu. It’s also just a good way to wipe the board if things are getting ugly.
Ashling the Pilgrim loves to have as many ways to deal damage to all players as possible. Molten Disaster is yet another way to do just that. For the same reason, Chandra, Fire of Kaladesh wants this Sorcery in her fold, as well. In Chandra’s case, she has Pyromancer’s Goggles to copy it, and Pyromancer’s Gauntlet to make it deal 2 more damage to each target.
Lastly, Rosheen the Meanderer loves any red and/or green X spell, since her tap ability adds 4 colorless mana to your mana pool to cast any X spell. Having 4 free mana to cast Molten Disaster makes it a really potent spell.
If you’re playing a mono-Red deck in a Commander deck, Molten Disaster is a good card to consider if you need a sweeper that can easily be made immune to counter-spells.