Headphone jack. Next to my bed is the one good Bluetooth headset, the two crappy backup sets for when it is charging, and the gigantic earmuff yardwork set for when the good one is still charging and the 2 shit ones have already died.

IR blaster in phones

In the gaming sector, nothing has adequately replicated the stylus used by the DS, 3DS, and Wii U. It was the best way to play a few signature games like Elite Beat Agents (now incarnated as Osu) and Trauma Center: Under the Knife. Touchscreens are just a bit too universal and resilient for us to go back to them.

Not sure if an automatic transmission qualifies as a modern gadget, but I remember push starting my car back in the day when the battery died.

I’m surprised I haven’t seen anyone mention IR transmitters in phones. Luckily, some phones are bringing them back (cough OnePlus Open cough)

Good keyboards on computers. At the office, everything are those extremely uncomfortable $5 dell keyboards. At a climbing gym or pool, the liability iPads that you sign forms on is using those really uncomfortable apple keyboards too.

I miss the better keyboards that we had back 25 years ago. Modern box jades bring some of that back for your own PC.

Memory card slots.

I can tolerate a missing headphone jack, a non replaceable battery, but a missing memory card slot is just too much.

At the moment, the only non Chinese brand of phones that includes this slot are Samsung I think. And even then, certain models also include it.

I'm sad that popup front cameras didn't catch on. I only remember 2 or 3 phones that had them. For me it's the perfect compromise - this way you can make an end to end screen without the need for a notch, and since I very rarely use the front camera, I wouldn't be too concerned about the durability of the popup mechanism. The only real downside I see is that it complicates waterproofing.

Things in general used to be made to last / hard to break.

The Nexus One had so many features I miss:

Trackball for scrolling

Notification light built into the trackball with customizable colors depending on the app

Back plate came off, replaceable battery

Small and a one handed wonder, the trackball kept my fingers off the screen

It was a replacement for my jail broken iPhone OG, such a better interface for me than the iPhones and it had very basic multitasking when the other guys could only do one app at a time

Edit: Formatting

Affordability?

My 1st phones were around €200, now you only find cheap junk that breaks within a year at that prize point. Having to cough up €500-700 for a phone that lasts a few years sounds excessive. Best phone until now is my '18 Nokia 6.1. Prize was €300 and it's still going strong.

I miss how gadgets used to be nifty and little. Every time I get a new phone now I have to stretch my fingers more and more just to hold it.

FM receiver on phones + 3.5mn jack was a crucial source of local radio transmissions. I suspect some phones still ship radio receivers but the popular types like Samsungs and iPhones don’t seem to care (or perhaps that competes with their music and podcast markets).

Oh yes the notification light was incredible. I had one on my Pixel 2 XL. I just switched phones like a week ago to a Nord N200 and it doesn't have one. Not too big of a deal though.

I wish phones still had IR blasters but those are long gone. It would be awesome to control my Edifier speakers with my phone as a remote control.

Edifier RC10E (Unofficial remote control for Edifier R1280DB speakers) https://f-droid.org/packages/ir.remote.edifier.rc10e/

Edit: Also how about a good camera? All mid range and low end phones today have like 3 or 4 mediocre cameras because it looks fancier then having 1 nice camera.

Size. I really don’t like the current 6”+ phones. The last phone I really liked was Google Nexus 5, because it had just 5" display.

Small Flagship Android Phones. Im just not a big fan of phones which doesnt fit into pockets :(

The ability to reach every part of the screen with the thumb on the hand holding it

Physical keyboards. I want a modern Blackberry that actually gets some half-assed OS support. Unihertz Titan was a neat one but had some quirks.

Lack of notch

A lot of what I'm seeing here is included on my Sony Xperia.

Headphone jack, notification light, SD card.

I do miss having a replaceable battery like my older LG phones had and stereo fromt-firing speakers like my HTC One M8.

My 2001 flip phone could schedule sms messages to be sent and it took smartphones a decade ish to add that feature.

Aren't notification LEDs somewhat obsolete now that we have always on displays? One advantage could be that they are less power hungry than keeping the screen / touch panel alive all the time. But in theory one could just create a permanent "notification LED" with an always on display, then it's the same thing from a user's perspective.

A built-in scripting language. The TI-83 line of calculators have an app programming language that requires you to side-load code from another computer, but they also have TI-BASIC, which allows you to write a wide variety of scripts right on the calculator itself. This should be standard on all 'smart' devices. It's so stupid to have gigahertz of computing power in your pocket and not be able to do anything without writing the app on another machine.

I know Termux for Android exists and that's a good start, but I'd like to see something baked right into the OS that has access to all my device's cool sensors and gizmos. The camera, the microphone, the aux port, the usb port, the accelerometer, the bluetooth antenna... all of those things should be exposed to the user. This would be a really good use case for 'visual' programming ala Scratch, since you could assemble a script right from a touch screen instead of having to plug in a keyboard.

The rotary disc on phones!