I'm aware of an "AI bubble" and the over-concentration on the "Magnificent 7".
What else is obvious to people and why is the timeframe (next 4 years) so obvious?
That's the obvious part. The consequences of that are anyone's guess, as is the timeframe. But it's not a sustainable situation, so something is bound to happen to change it eventually.
People have been claiming the end is near since forever; economists have been saying for months now that stocks should already be falling, but they are going up. And also, it feels good to be part of the in-group that just knows more than everyone else. Just ask a prepper: they will be equally convinced.
So in summary, even if we’re headed for another crisis, unless you’re only a few years from pension, you’ll just sit this one out calmly, just like all crises before. Unless the global economy breaks down for good (in which case you’ve got other things to worry about), your ETF will recover. Don’t let the fear mongers get into your head.