There's no multiverse in which I'm saying I like Atomic Blonde more or as much as Get Out. My point is that word of mouth is mostly a non-factor now, and in any given year it's really only helped maybe one or two movies. For example, The Others famously opened weak but became a box office hit over an incredibly long period, solely because of word of mouth. But word of mouth didn't appear to play a major part in other movies that year, and more often makes something a cult classic long after audiences blinked and missed it.
So it's not some ever-present element. It's once in a while, and seems to usually matter more for lower-budget movies than for blockbusters.
But to get out of the weeds here, my point is really that there's just no quantifying quality based on box office. That doesn't work. The only thing you can maybe associate box office with is mass appeal, but even then the marketing is a non-quality-related factor, so are the competing movies in the same opening weekend, whether it's R-rated (keeping a lot of the younger, walk-in "let's just go to any movie" audience out), etc.
Or, put another way
The Last Temptation of Christ made $33.8M when it opened in 1988.
The Passion of the Christ made $612M in 2004.
Adjusting for inflation, Last Temptation still only made about $54M in 2004 dollars.
If you want to argue that box office is an indicator of quality, not a whole slew of other business decisions and random factors, I'd love to hear how the numbers show that Mel Gibson's blatantly anti-semitic and ultraviolent vanity project--whose marketing efforts included helping evangelical communities organize bus trips for parishioners to see the movie en masse--is clearly a better movie than Scorsese's.