If I were to guess – it’s the look of the film.
That (VFX) over-glossed aesthetic is not helping ticket sales at all.
The original was a low-budget Australian picture, gritty, and grounded in realism – being of the exploitation era of filmmaking, the first Mad Max was shot with camera/lenses that were extremely low-grade. This ensured it had a “mockumentary” feel and look, even though that’s not the genre the ‘Mad Max’ films belonged to. The closest comparison I can think of is Dennis Hopper’s ‘Easy Rider’ or ‘Texas Chainsaw Massacre’, both titles heralded the revolution of independent films in the 70s. Then as budgets inflated; each subsequent release became more slick and polished, continuing to this day with the latest entry, ‘Furiosa’.