This change also impacts the Expertise cycle (which will no longer be able to cheat split cards into play with their "cast for free" ability), Goblin-Dark Dwellers (which can no longer flashback a Boom // Bust), and some other less popular cards as well
It can combo with cards like Living end and Crashing Drawbridge for a one-turn kill or just be a one-card value engine
They (usually) provide a power and toughness boost to whatever they enchant as well as other small benefits, such as adding a scry to your attacks or giving a creature ward
The lower the bracket, the more casual and focused on 'doing something neat with friends' the deck is
While it is ultimately arbitrary, here is what I was considering when ranking the cards: Use Scenario: I took into consideration where the cards will be used, for example Commander deck cards are considered in that sense, while uncommons in the main set had more thought put into limited usage