I see this from a slightly longer perspective. Audax has been around a long while, picking up from Tourist Reliability Trials back in the day, and now there's a pushy new kid on the block in the corm of cyclosportives. The magazines think it's 'cool', the retailers certainly do, and there's money sloshing around there that's never going to get to the rain-sodden audaxers over their beans on toast.
But I was involved in something similar a few years ago. The Rough-Stuff Fellowship is a venerable institution that's been around a long while, and there was a lot of off-road riding before that (in fact, if you go back far enough, most roads would qualify as 'off-road' in today's criteria
).
OK, so in the mid-80s, there was a wave of Yanks coming over here with flashy bikes that they used for mountain biking. Hey, what's that? Haven't we been mountain biking all these years? Do we need the car-worshipping Septics to show us how to do it? Surely not. And, if we let them in, won't roughstuffing collapse?
And yet, for better or worse, MTBing is here to stay, and a popular pastime, generating huge turnover for bike & component manufacturers, and ad revenue for magazines that wasn't there before. So what of the RSF? They're still going strong, and riding hard. You just need to see Simeon's regular posts of the South Lakes Group to see how they are thriving.
But there were times when it was anathema to turn up to an RSF ride with an ATB, and suspension would have been met with gasps and tuts. Now, they ride all sorts of machines. And it's fine.
I doubt the readers of MBR, wanting to grab some gnarly air on an awesome downhilling whatever blah blah blah would care about even the existence of RSF, and nor are they likely to be reading MBR. But they co-exist, serving different groups, and life goes on.