What is special about films from 1930's....

It would depend on how one defines pretentious, because while I don't have much point of reference as I haven't seen a lot of films from the 30's, mainly clips, they can look pretentious. I get the posters point.

pretentious
/prɪˈtɛnʃəs/

adjective: pretentious

attempting to impress by affecting greater importance or merit than is actually possessed.
"pretentious art films"
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Similar:
affected
ostentatious
chi-chi
showy
flashy
tinselly
conspicuous
flaunty
tasteless
kitschy
overambitious
pompous
artificial
flatulent
inflated
overblown
overripe
fustian
hyperventilated
mannered
high-flown
high-sounding
flowery
grandiose
big
grand
elaborate
extravagant
heroic
flamboyant
ornate
grandiloquent
magniloquent
bombastic
turgid
orotund
rhetorical
oratorical
sophomoric
highfalutin
la-di-da
fancy-pants
posey
pseud
pseudo
poncy
toffee-nosed
dicty

Many of these synonym's do appear to fit from my own observation. I could be wrong, but sometimes if someone loves something, they may not want to hear anything that might taint that image, even if there is some truth behind it.