We only have two "smart* things: when we get up to pee at night, a motion sensor turns on a light in the living room. Much dimmer than those premade motion activated lights, so we don't wake each other. Returning to bed and triggering the sensor again turns it off.

And when it has been raining more than a certain threshold in the past 24h, the outlet into which the pump that feeds our drip irrigation is plugged turns off, and on again when it hasn't been raining for a while. Saves lots of water, especially when we are on vacation. (The rest of that system is " dumb", though.)

The only thing I'd need to make smart is my box fan, because once I fall asleep it would be better to turn it off, but I like falling asleep with it on, and I can't turn it off if I'm already asleep.

So I could make that a smart device.

But I got those outlet power adaptors with a mechanical switch timer that just turns the power off when the timer dial rotates. It's got a 24 hour dial and multiple pins, so I could put my fan on a schedule if I wanted.

Cost like $5, I've been using them since 1995. Easy to repair and replace.

If it ain't broke.

I could give you a bunch, but it would be missing the point: you should automate to fulfill a need. You don't need automation so there's no argument to make for it

Most rooms in my house each have at least a handful of different, indirect lighting solutions. I could pay an electrician to wire them all to a single mains switch, but then I would need them to come back whenever I want it changing. It would also be more complicated to have dimmers and set programs for different times of the day to to adjust the lighting to a number of presets.

I could just have the one or two overhead lights that these rooms came with, but that's just an unpleasant to look at experience to my eyes all of the overhead lights got replaced with ceiling fans that have no lighting that come on when the room is occupied and over a certain temp.

You walk in the room, a bunch of lights and may be a fan come on at the right lighting for that time of the day, then they go off at a suitable period of time. I even have all my garden lighting coming on via motion despite some of it being a separate 12v system that's battery and solar powered via a 12v zigabee multi channel relay.

If you have solar panels you can turn on appliances or compute intensive tasks if they produce power.

If you have humidity problems, an alarm can remind you if aerating makes sense. If you additionally have a bad landlord you can prove you aerated three times per day and still mold did grow, so he has to fix something!

If you have a home theatre one button can dim the lights, turn on the TV, and close the blinds.

You can have your motion controlled floor lights only turn on red in the night.

Small things which are in total useful.

With HomeAssistant its easy to do without any cloud connection.

By a curious turn of life, I have enough technical expertise in the right areas to be able to design the software and most of the hardware turn a lot of my home smart like that in a safe way were I'm fully in control of it all (no 3rd party involved) ... and I can't be arsed, for very much those reasons.

I mean at one point when I was playing around with microcontrollers I was looking for ideas of things to do with some neat microcontrollers which are cheap and have built-in WiFi support and I just couldn't find anything worth the trouble, for pretty much the kind of reasons you list.

Sure, lots of things can be done which are "cool ideas", just not stuff were the whole "remote controlled from my tablet" actually significantly reduces the effort in doing something without introducing new problems (i.e. it would be a whole lot of work to get my apartment door to automatically open when my face is detected outside and then the thing has a non-zero rate of failure even I I train the AI really well, so when it fails I would be stuck outside hence I would still need to carry a key around, so in the end it's really just less hassle not do it and to keep opening the door with my key), plus often the problem is that once you add "remote control" to a device's design you just make it consume a lot more power, so now it has to run from mains power rather than run from some batteries that will last for a year or so.

The maximum home automation I ended up doing it is automated plant watering and that stuff has been designed without remote access exactly because it can run from 3xAAA batteries for a year even though it actually has to power a water pump which when it's running does consume a fair bit of power (but it only runs when the soil on the vase is not humid enough, which is so seldom it averages out to very little power). Sure, it would be "cool" to read the humidity sensor from my tablet and activate watering remotely, but that doesn't actually achieve the point of of automated plant watering - making sure my plants don't die of thirst because I forgot to water them - whilst overall making the design worse because now it needs a lot more power and I don't have a design anymore where I can just replace the batteries once a year or so.

doorbell cam is just about the only thing i can think of

One thing I want is for my washing machine and dishwasher to coordinate with my water softener to be sure there's enough soft water left so that no hard water will go through them and to immediately initiate a regeneration if there isn't while the appliance waits for the regeneration to finish before starting.

My living room has no hard wired lights, and only one plug is on a switch. Only one standing lamp makes the place gloomy, but the second can't be on a switch. Rather than turning them on and off separately, I smartified them so I can do it via voice or app. Also if I'm cooking and my hands are a mess, I can ask Google/alexa/whoever to set a timer, add something to a shopping list, or tell me what temperature something needs to be. My favorite use is casting computer audio to multiple speakers so I essentially have a home sound system. Makes cleaning more fun. Also not having to get up to turn the bedroom light off at night is transcendent.

Nothing I use smart stuff for is particularly revolutionary, but it's handy enough that I like having it.

If the sun is up past 8pm && person home close the blinds could be a reasonable example. If water is flowing to the bathroom run fan for 30 minutes could also be reasonable. If motion near front door take photo of door and email/text it to you could be a rudimentary form of security or knowing a package arrived.

We turn on our vacuum robot after we leave because the kids are scared of the sound :0) but they eagerly help press the button on the phone to turn it on