Popular options include Atraxa, Praetors Voice for control and counters, or Edgar Markov for fast, aggressive vampire builds
However, their effects proc so long as they die when they were a creature , meaning if Zur turns them into a creature after they used their effects, if they die again they'll go back to being an enchantment
In effect this means you are losing a bit of card advantage to gain the tempo which is generally a fine thing to do
In other words, Proliferate lets you put more good counters on your cards which already have good counters on them, and put more bad counters on your opponents stuff with bad counters
While Ragavan, Nimble Pilferer has been looking more problematic and especially unfun in Vintage and Legacy (banned), its still relatively balanced in Modern