I like the mini too, and I have one, but it didn't sell well.
Here's the thing nobody talks about anymore, though. The conditions it launched in weren't ideal to make a fair assessment of how it would sell today. A smaller, more mobile device is great when out-and-about.
But the mini launched in 2020. Many people were either laid off or working from home, and in general, not traveling. A large Pro/Pro Max phone that doesn't fit easily in pockets is more palatable for use around the house, and a lot of people likely made their purchase decision in 2020 with a device in mind that fit the needs of the moment. In addition, the mini was poorly promoted, it definitely came with other compromises (missing the telephoto lens, ProMotion, and of course the smaller battery), and even the name is quite diminutive. And don't forget that it launched just a few months after the second-generation 4.7" SE, robbing it of potential sales for those who would have preferred a smaller device with fewer compromises. But that aside, I think there's a growing large phone fatigue as phones have continued to get bigger and heavier since then. Just look at the 17 models going back to aluminum and gaining back much of the weight that was shed when Apple dropped stainless steel for titanium.
I'm not going to pretend that it'd break any kind of sales records if it were reintroduced today. But the mini came at a bad time there was a clear misunderstanding between the folks who wanted a less expensive iPhone and were disappointed that the mini was a full blown base model iPhone at a base model iPhone price instead of it being another SE, and people who wanted a smaller Pro model and had to choose whether to accept the hardware compromises of a base model iPhone to get the reasonable size and weight.
I think the low-budget market is adequately addressed by the SE/16e and those who wanted the mini to be another SE were misguided. But the larger market for iPhones skews heavily toward the Pro models. Yet, Apple continues to ignore the Pro market for anyone who appreciates the Pro camera system, and until this year, the ProMotion display; but doesn't want to lug around a 200g brick that sticks out of most jeans pockets and is uncomfortable to hold for more than a few minutes without a Popsocket or some other contraption.
I get that there's only so much space for the hardware in a smaller form-factor. However, it would be completely reasonable to put the 17 Pro hardware in a 5.8" body, even if you lose a little battery capacity, and make a Pro model that's more comfortable to hold and carry. Similar to the 11 Pro, which was the smallest of the iPhone 11 models. But Apple refuses to make an iPhone below 6.1" now, so we'll never know how it'd sell under non-pandemic circumstances.
