I think they have done some pretty neat things with 5e but they are off on their priority rankings idea.
Mearls said:
A priority ranking for D&D is a list of character option categories, such as classes and proficiencies. The priority ranking places the most important elements at the top of the list and the least important ones at the bottom. In terms of D&D’s content, classes sit at the top of the list, followed by races, spells, backgrounds, and feats.
The ranking answers the following question: What wins in a contest between option A and option B?
If my class gives me the ability to become an awesome archer, I should be a better archer than other characters whose classes give them no archery ability, but who took feats or can cast spells on themselves to gain that ability. Class is ranked higher on the list than spells or feats. Therefore, class wins.
First, it depends what it is you are talking about and this list is mixing apples and oranges. I will assume he is talking about "class features", "race features", and "background features", if so, then we are on the same page. You would never weigh a whole class against one feat or spell. That said, this is insightful into their design approach. I would have mixed it differently.
A Background feature
A Race feature
A Class feature
A Spell
A Feat
The reason I feel the background, albeit it does little, it is the biggest character choice when finding your PCs place in the world. So your choice should matter. This will provide your proficiencies which are key to your overall character concept and mechanically give you a tremendous amount of abilities. Example if stealth all the time whenever you want is important to your character concept pick a background that gives you this proficiency.
Then race is the next big choice. It gives you similar stuff similar to background.
Class is third, it is the mechanical construct you make your way in the world with. It also provides your biggest set of abilities. It can also add to the two choices you already selected.
Then feats and spells. These, if it were my game to design would be two halves to the same coin. Any supernatural ability would be a spell and any non-supernatural ability would be a feat.
One other class design point too. I would strip the class features out of classes and give them feats/spells instead. If it was a supernatural ability, add it to that classes spell list. If it was a non-supernatural ability I would add it to that classes feat list. Spellcasters get lots of spells and non-spellcasters get lots of feats. Then there are lots of 1/2 and 1/2 classes too. Simple design. Not the direction they went but hey...