Hehe. The meme's are trollin' no doubt.

Still, the linked analysis only solidly supports an assertion that the story unfolds sometime after 1986. Mad Max can be set 2021-ish.

The original Mad Max film was made in 1979 and features the opening tagline “A few years from now” which leads us to assume that the story takes place some time in the mid 1980s.

No. I don't assume narrative references to timelines in speculative fiction are relative to production dates. I take phrases like "a short time from now," "a long time ago", and "once upon a time," to fix the setting in reference to the audience's present.

Mad Max is always set in an apocalyptic future — even if you're literally living through it.

This to me is part of what makes the memes funny and relatable.

I don't think this is a definitive 19XX. The "1" is debatable and the "9" ephemeral. Remember we're looking at a still here, but the original moving presentation is meant just to be glimpsed, not read. In the accompanying dialog the children chant the inscription, omitting the date altogether.

These numbers were intentionally obscured to leave the timeline wide open, not open to a decade or century. If any precision were necessary then why not fix a year outright.

Moreover — even if it were 1999 at the latest — there's room for interpretations where decades have passed since the departure of Walker from Planet Erf because, as Savanah puts it:

It's the story of us all. We got it mouth to mouth. So you gotta listen it and 'member. Cause what you hears today, you gotta tell the birthed tomorrow.

This young cargo cult is clearly procreating. The oldest of them appear to be in their late teens or early twenties. It's suggested they're recounting an oral history rather than events remembered first hand. They seem to have been infants or not yet born when the rescue party left them there...hm, also weird that it's a "rescue party" and not a "search party" — maybe that's an Aussie thing, dunno.

Anyway, Hollywood's version of extended canon for this franchise carries no weight with me. I don't even worry whether Fury Road takes place in the same universe or an alt. It's got flamethrower guitars though.

Mileage may vary by POV. I applaud your skepticism.