Now that’s a pretty good point. freeze by itself is bad. Consistent freeze, however, is plenty capable of locking the opponent out of the board.
Thing is, most classes can create plenty of threats beyond the range of their 30 cards decklist, and the minion size/mana cost ratio grew a lot in the last years. If mage isn’t capable of discovering and stalling for more discover, it imply can’t keep up.
It can be argued that it makes for a miserable experience for the opponent when the mage RNG his way out with an answer, but god, i will tell you that if mage had some straight power cards and draw to use them, they would.
Hell, mage can barely find space on the deck for straight removal since the tempo competition is so fierce. Most removal in mage decks is discovered.