Obviously, the "Companion tax" significantly blunts the power level of all Companions. But I agree with @MaximumCDawg that they still retain many advantages.
Consider Lutri for instance. You don't rush an early Lutri---you summon it in the endgame as a win condition, or after the early game has wound down and the opponent is out of countermagic, for a particularly backbreaking sequence of plays or grindy Karakas shenanigans.
By the time you're ready to summon Lutri, how often have you passed at least one turn with 3 mana up that you didn't need for anything else? Probably quite often, no?
So I don't think Companions have been killed, by any means. Though you probably won't be using Lurrus to combo-kill on turns 1 or 2.