You can objectively gauge how difficult a certain shot is to pull off or a certain multi rhyme scheme. Now it may not hit for you subjectively, but there is an objective component to all artistic works... What tools were used, how much time when into it, how common or uncommon the themes or subject matter is etc. Successful ambition and risk taking tends to score better with critics as we're often looking for the next "new" thing and want to reward creativityWhat do you mean by "looked at"? Does that include evaluation?
I find that the only true objectivity when it comes to art is very limited, since it's meaningless for evaluating art and comparing pieces, but this is always what it's used for.
I agree that too much comparison takes away from the conversation, but you don't want to get caught comparing the craft of a Dr Dre album to a mixtape recorded in a day in a bedroom. You might like one or the other for your own taste, but there are many objective factors that differentiate the two