Having one try and doesn't fail is more impressive in my opinion.
Sacrifice - Risk - Opportunity. Something that a spamable cc doesn't promote, at all.
In this xpac, now, a 6s CD on polymorph would be the best way to "fix" mages until an entire rework.
If Mages are squishy again and only have polymorph (and I guess deepfreeze), then not getting polymorph off is huge because the Mages team is not getting counterplay while under pressure themselves.
Spammable CC isn't an issue when due to pressure by the other team (again, active not passive) windows within which you can get your CC off are limited and counterable.