You don't just need "someone". You'll find "someone" say anything, including that the Earth is flat, its 40,000 years old, and we're controlled by lizard people. The standard isn't "someone". You'll find someone who claims a table of ICD codes or a stop sign appeals to their prurient interest and is sexual in nature.
You'd need "the average person, applying contemporary community standards" to say that under the Miller test and have the court/a jury to agree. Not just any person applying any standard.
No, you just need the court to agree, you don't need to actually get the (non-existent, fictional abstraction) of “the average person” to say anything, you just need a judge to believe that.
https://en.wikipedia.org/wiki/Reasonable_person
And other similar "vague" concepts arise elsewhere in the law, like someone "skilled in the art".
https://en.wikipedia.org/wiki/Person_having_ordinary_skill_i...