You did. You had eight, you unlocked four. Your crown store UI will be grayed out and say Fully Upgraded until Morrowind, when two more will become available.
I finally found my favorite main class to play after trying them all and I only have four slots used. I couldn't imagine having all of them decked out like my main is. Too much work!
I'll be making a Warden of course so I might find out it's my favorite but I doubt it because becoming invisible and sneaking around is too fun. I don't have the time to use up all my slots.
All 12 are maxed, 50 in every profession, equipped with all Legendary gear, fully maxed out horses, all have mages/fighters guild 10 and many even have 9 traits researched.