I would sort propaganda posters in the same category as commercial advertisements.

Some are good, some are bad but there usually is a certain degree of artistic skill involved (think about "keep calm and carry on" or "I want you")

E.g: scrolling through this list one can see examples for both cases.

https://content.libraries.wsu.edu/digital/collection/propaga...

In my view, such skill with painting is largely mis-labelled as creativity. It's pretty much a technical skill. The design and subject matter of the posters are where the creativity lies. The two things often get conflated, perhaps because of their joint use in the creation of great paintings, but they're fairly separable.

I would put it a bit differently: A lot of great art has simply been applied craftsmanship. The idea that art has to make a statement or the like to be art, per se, is a fairly modern notion, and often helps excuse zero craftsmanship nonsense like a Finnish "artist" dumping a bunch of blood and shit into a washing machine and calling it art.

"(also, categorizing propaganda posters as art, ewwh...)"

Heinrich Heine, the german Poet declined working for the socialist party despite symphatising saying something like:

I want to remain a poet, you want a propagandist. A poet cannot be a propagandist at the same time.

Art for much of human history was devotional, a lot of our greatest artworks today are still religious in nature. The idea that art solely is an act of rebellion rather than say worship, is a pretty modern idea that has produced some rather questionable art by the way.

Of course a great artist or poet can be a propagandist. Riefenstahl, Mann, a lot of German nationalists were great artists. Whether what they endorsed was moral or not is a different question.

"The idea that art solely is an act of rebellion rather than say worship"

I did not say that and neither did Heine.

Most of his works were political. But this is not the same as propaganda, which is more like advertisement. With the tools of lying, deceiving and manipulating.

And whether "Triumph des Willens" and alike qualifies as art, I have a different opinion.

There is a difference between devotional art inspired by religion / mythical events long past (Aeneid etc.), and between the sort of propaganda that the modern totalitarian state demands, which usually centers around some living or freshly dead leader.

I'd be open to discussion where the exact limit is. Lenin died in the 1920s, Marx even earlier, but those two were frequently depicted in Communist propaganda of the 1980s.

So it is probably "hundreds of years".

Soviet bus stops are another great example. Most Soviet architecture was forced to be very utilitarian, but bus stops managed to be the rare exception and thus got a lot of creative energy

https://www.wired.com/2015/09/wild-architecture-soviet-era-b...

https://www.boredpanda.com/most-peculiar-soviet-bus-stops-ch...

on your parenthetical, you can see the artistry in the pure visual expression no matter how loathsome the subject matter.