I'm not fully convinced. I'll tell you why. You may not like it.
Firstly, your name is 'rapsucks'. Insomuch as I agree, you need to grow up (however old you may be).
Secondly, Dean Martin and Jerry Lewis were B-movie comedians - even then. They were annoying and quaint and though it was a nice pairing, they are not a duet (arguably alone or as a pair) that one would reference as a comparison to 'appreciate' "Intolerable Cruelty".
They were funny. Lewis was a good comedian on his own (though pretty annoying in most instances and nothing 'fantastic' or genius) and Dean Martin was...well...Dean Martin. I know them (not that those criticizing are 'too young' in this case) and I still don't think this film is any good. Matter of fact it is downright shameful to what the Coen's are capable of.
Does that satisfy your 'inkling' as to the age of viewers?
This movie wasn't just the Coens it was also Brian Grazer who works with Ron Howard and one of the writers was one of the Creators from South Park(Matt Stone)that's the reason it' different from other Coen movies.