I played with HomeAssistant for a while, and I kind of liked tinkering around with things, but it was still a huge pain in the ass, and I have no delusions that it was saving me money or time. For someone going into this with the expectation of tinkering, it's fine. For a commercial venture, I don't see current 'smart home' products/services as very viable. I've already switched my light bulbs to LEDs; how much am I actually going to save by having them turn off automatically after a preset delay? Not much.

One of my DIY projects was a couple smart plugs and a temperature sensor; at the peak of summer heat, when the house was hot but it cooled off at night, I automated ventilating our house. It had a great impact on our comfort without using air conditioning (which we didn't have). That is a decent use for this kind of stuff, but it's far too much effort for most people to go through.

I have learned that almost any effort is far too much for people to go through.

I feel slightly the same. But I still see some value in some actors but not really for smart solutions. I don’t need a central tablet to control the lighting in the house or play a music in every room at the same time etc. These are nice applications but the burden to pay and set it up and then actually using it would be to much. I got me some Shelly Relays to retrofit some light and Rollo sockets. The only “automation” I programmed is to open all Rollos in the morning at 8am. I really hated it to go from room to room and press the button next to the window. Classical first world problem. I also programmed my Harmony Remote to control the blinds/Rollos and the lights. Nothing smart just a button that does the same action the button in the wall can do. Ok the blinds can now be controlled in percentages which is nice. But and here comes the but. The setup is so custom and involves 3 software pieces that I lost a lot of interest while setting this simple system up. The harmony bridge to a custom piece of software found on GitHub which talks to openHAB hangs constantly ( something with harmony hub losing Wi-Fi access every few days). The setup and management of the Shelly plugs is also not ideal. One can flash them with a custom firmware but I wanted to start with the stock firmware first to feel the water. All in all I kind of like the topic of home automation but I’m just to lazy to play zookeeper for a bunch of devices. And the mentioned providers with their vendor lock and cloud only solution will not get into my house.

There are plenty of useful/interesting things, e.g. reactive lights, more proactive climate control, controlling ventilation on demand, presence based interactions etc. Some of this can be achieved with dumb solutions, e.g. humidity controlled switch etc. But when you start integrating devices together they can coordinate to do much more complicated and "smart" things.

Does everybody want to do that? No. How far do modern systems go towards achieving any of that? Ehh, IMO not very far unless you put a lot of effort into it. Do the UIs of modern systems really make setting up these sorts of complex interactions up accessible for the average person? Nope. Are there glaring privacy and security concerns? Yep. There are lots of perfectly valid criticisms, especially of "smart" homes as they are, but there are certainly lots of possibilities.