I own a high-quality mirrorless camera and several thousand dollars worth of good lenses for it ranging from a very nice wide-angle to a stabilized telephoto. But in practice the current iPhone Pro cameras are good enough that I rarely get it out.
Part of that is the "the best camera is the one you have with you" adage, which is extremely accurate. But at this point, between the wide lens, high-resolution main, and decent zoom on the telephoto, I can take photos over a much larger portion of the range of my "real" camera than was the case in the past; with all the computational stuff, the photos I get with my phone are not anywhere near as dramatically better as they used to be; and the low-light stabilization and stacking is good enough that the larger apertures and large, stabilized sensor on my "real" camera is no longer the absolute must-have it once was.
Basically, there were pictures--telephoto, wide angle, low-light--that it was possible to take with a dedicated camera and impossible to take with a phone 10 years ago, while the list of things in that category has shrunk dramatically, as has the relative difference in quality of the resulting images.
One of the big remaining items is high-zoom telephoto; the high-res sensor and folded lens on the 17 Pro is a big improvement, but it still has major limits that a big piece of glass on a big sensor does not.
Bolt-on lenses like this are, as a result, really tempting... but having to use their case to attach it, while understandable, is an absolute deal-breaker, and at the point I'd put this big chunk of lens in my pocket I'd probably be just as likely to go and get my dedicated camera, so other than slight convenience in the pipeline it's just not going to give me anything I'll use.
(An aside, the iPhone's exceptionally good automatic HDR is probably its biggest advantage over my dedicated camera, and not to be taken lightly; in challenging lighting situations even with better-than-8-bit dynamic range on my "real" camera the iPhone takes better and more usable photos without having to do any tweaking or adjusting. It was some time ago, but I was in Death Valley in a canyon that had really extreme light differences between the shadowed walls and the sunlit side, and despite having my big camera around my neck I eventually gave up and started using my phone because it was taking better photos. With a tripod and a lot of time, had I been aiming for a professional art shot, I could have taken a range of exposures and post-processed into a good HDR image, but I was trying to enjoy the vacation and take some nice images to memorialize it, not sell a print.)