So I dug out the old DSLR and brought (lugged?) it with me on a recent vacation to Peru. I threw in the largest SD card it would accommodate (32GB), which gave me literally thousands of photos at the highest quality JPEG setting (don't really want to deal with post-processing RAW images). The only lens I brought was a 35mm 1.8 DX lens.
I have to say that the quality of my photos was much better than I had seen in quite some time. It is hands down better than my smartphone. Even though they are both ostensibly 12MP, the larger sensor and lens make a big difference. The two things I missed from my iPhone were super wide angle shots and low light. Since I had my iPhone with me, I could just pull that out if needed.
I briefly thought about buying a new DSLR or a mirrorless, but really my old one is good enough. I will probably just buy an 18-55 zoom or something for my next vacation.