Sort of...
I thought about doing it two years ago when my son was born. My DSLR was outdated and I had been on a hiatus from photography for a few years, and the iPhone 7 Plus with its dual-lens system seemed versatile in ways that smartphone cameras hadn't been before. I used the iPhone like crazy, but ultimately upgraded my DSLR. At first it didn't seem like a huge deal, but it quickly became clear that in anything but absolutely perfect light the iPhone's photos appeared a bit blotchy, lacking fine detail and tonal transitions. I regret that the only newborn photos I have of my son are iPhone photos. They're better than nothing, but when my second child was born I brought the "real" camera with me, and comparing the two, it's a night-and-day difference.
I still use my iPhone very heavily, but it has become my dedicated video camera instead... and that's largely due to the H.265 compression on the videos. If my "real" camera did H.265 as well there's a good chance that it would be my primary video camera, too.
The iPhone 11 Pro looks very nice, and I am very tempted to upgrade my 7 Plus for the video options that three lenses would afford. I have no doubt that the phone also handles better in less than perfect lighting, but honestly I'd be shocked if the photos didn't lose detail quickly once lighting became less than perfect. I do not intend to replace my camera with it. I don't mind carrying my camera with me to most places; I would hope that the iPhone 11 Pro would make me feel better about leaving my "real" camera at home a bit more often, but I wouldn't hope for more than that.
But as usual, YMMV and all that. Most of my photography is done indoors these days, in fairly poor lighting. I also have a toddler, and rely on extremely quick autofocus. I'm fairly certain the iPhone won't perform well for me - not for the quality I've come to expect from my photos. But if you're primarily photographing in bright conditions, and/or you find it a hassle to take out your camera (whether due to size/weight or workflow), then it's just a waste. As the saying goes, the best camera is the one you have with you. I'd add, "the one you end up using" to that saying as well. The 11 Pro is easily the best camera system Apple has included in their portables, and three lens options are incredibly nice.