. My argument is that for a Wild Mage to compete against a Draconic colleague, she needs to use Tides of Chaos once for every spell she casts. That's right, if the sorcerer has, say, 15 spell slots, she has the capacity to gain advantage sixteen* times during the day, and she needs to use every single one of them.
*) not counting various other ways to cast more spells, such as Sorcery Points
But Tides of Chaos state once per long rest...? Yes, but it also empowers the Dungeon Master to have you Wild Surge after casting a spell. And this is the core of the trap.
This is sufficuently hidden so many players don't realize they need to make sure their DM is onboard before choosing the subclass. And that many Wild Surges goes against the instincts of many DMs. The end result is that yes, it is likely the Wild Mage is "as terrible as it seems", even though many posters might post anectdotal experiences to the contrary.