It started life as a perfectly servicable Android phone. A little on the slow side, but not drastically so. The main problem was its 384MB of backing store. By 2015, very few Android apps supported installing to the SD card, and Google Play Services managed to eat almost all of the available storage.
Ideally, I'd like a modern phone with the same size and build quality of the Xperia Ray, the phone that fits unnoticably into my pocket and survived countless falls onto hard floors. I don't think it even needs to be super fast. Just with enough backing store to function as a modern Android device.
And knowing that such devices are possible is the reason I don't agree with the "you'd probably be fine with a feature phone" answer.
At the moment, I'm using a Z5 Compact. It's a great phone with solid build quality, but it's still too big IMO.
It's incredible, but all companies go in the same direction. In the very few instances when they do innovate, they go in really odd directions (curve displays, in-built projectors), but they don't address basic stuff like size or physical keyboard.
Of course, it fails in the "cheap" dimension, and also on "size" and "replaceable battery" ones. Still, as far as things that would be considered compact in the current smartphone market, it looks like close to the only option.
My SE is 124 mm x 57 mm x 7.6 mm. My previous phone, a Moto E, was 125 mm x 65 mm x 12.3 mm. The Xperia X Compact mentioned in another comment is 129 mm x 65 mm x 9.5 mm.
Personally, I fit your description to a tee. My phone is a Samsung Convoy 2 (the 3 and 4 are inferior) from ~5 years ago. My camera is a small Canon EOS 1200D/Rebel T5. Even the cheapo 18-55mm kit lens that comes with the camera takes better pictures than an iPhone 7.
The cheap camera paired with a cheap prime lens (I paid $90 for a CEF 50mm f/1.8 STM lens) results in jaw-dropping clarity and dreamy depth of field blurs that no phone will ever match--until we overcome the physical limitations of current camera technology requiring light to shine onto a sensor.
The Convoy 2 packs a camera equivalent to an iPhone 3G. It gets the job done fine in daylight, and is passable in dark settings. The LED flash is almost excessively bright.
Personally, I have no problem carrying both with me. The only time I'm surprised by something I'd like to take a high-quality picture of is of another car I see while driving. So even if I had a 2016-level smart phone, the picture's still going to mostly be of a dirty windshield and my car's A-pillar. (Plus, you know, the whole dangerous and illegal caveats.)
They make much smaller cameras than mine that still take great pictures. I suppose someone out there really does drag around both devices with them. I'd expect that number to increase somewhat as mirror-less interchangeable lens tech continues to rapidly improve.
Mine can't, but there are dozens of great models that can, as I alluded to. http://www.pocket-lint.com/news/120768-best-compact-cameras-...
So maybe you, the OP etc just need to understand that your requirements are niche and unlikely to ever be met in the more popular phones.
- No built-in mobile hotspot functionality, and no 4G/LTE
- No ability to use messaging systems other than SMS (Google Hangouts, Slack, etc.) except for maybe a few whitelisted ones
- No mobile maps
None of these would have been a dealbreaker 10 years ago, since no phones supported mobile hotspots or 4G or LTE, people either used SMS or some IM system that your phone did support (e.g., AIM - although AIM also had a pretty good SMS bridge, back in the day), and nobody expected you to have maps on your phone. Today all of those expectations are different.