It's actually a sound strategy. Think about this, someone chooses to rent cards first and figures out the strategies that work best for them and purchases the cards that work for their style of play. Purchasing packs leaves much up to chance and there are cards that are simply not what fits what a player uses best.

Not every card is "good" nor does every card possess an equal amount of present and future value.

There's a lot of pressure to purchase Chaos Legion packs and play in the Modern Format. I'm doing neither. It does not mean that there is a lack of faith in the development team or in the ecosystem, it is just that it is not my strategy.