I think that the critical element that makes something meaningful is
the passage of time. Sure, the avant-garde is great, but
only time tells what elements of the avant-garde are passed on, are
assimilated, and find currency with the next generation of avant-
garde.
Tragically, that is why most great artists are only appreciated after
they die--because it takes that long for a truly avant-garde artist's
ideas to find some place in
a new generation.
I do take exception to the idea that only avant-garde work is good, or
admirable--or rather, that work must be incomprehensible to the masses
because it is so far ahead of its time. I think that some of the
greatest works of art, design, music, etc. are easy to understand (at
least on some level) for everyone. Besides, I do think that only truly
great design actually can be understood by many people--even across
cultures. Yes, it must touch those universal truths, but it is not
easy or simple. But I reject the notion that it has to be
incompressible.
However, how long should the comprehension take? minutes, hours,
years, generations? I think that the best work invites significant
comprehension on several timeframes--Beethoven's symphonies can be
enjoyed in the very moment for the experience, but also invite deeper
contemplation over repeated performances.