My thinking mirrors yours. If the market is being propped up, it's to maintain a status quo, not push things higher. That means we're at some sort of ceiling.
I tend to be very bearish though, and was sat in bonds for the 5 years or so preceding this march run-up (where I went 50% into equities and caught a nice ride), so I'm usually a chicken-little investor, and I am second-guessing my fearfulness.
But I keep looking for that exit door to return to my comfy sideline bench. I just miss a lot of gains that way.