Overall, I see little sense in the typical smart home functions.
I am completely with rick2018 on this, you quite obviously confuse remote controllable and automated (let's just leave the "smart" aside, it only causes confusion, your questions are the best proof).
Even this statement of yours alone offers plenty of room for speculation and confusion. Because in my experience, what you consider typical functions are child's play for someone else and futuristic for a third party. I want to imply that there are no truly "typical functions," since even in lighting alone the range is so wide that nowadays you basically need a doctorate to grasp everything.
The devices that can actually be sensibly controlled via app,
Basically an oxymoron. Nothing that can be sensibly controlled basically needs an app. Because it suggests that before the pre-smartphone era there was nothing and everyone had to wait until this liberating device was finally invented.
In every room, there are corresponding light switches or motion detectors.
Yes, and now imagine in an automated house these end devices communicate with each other and with the lamps and with all kinds of other sensors. The resident only needs to reach for the light switch if something does not go according to their liking... and that should then happen very very rarely in a truly automated house. Almost as often as a solar eclipse occurs. That’s the whole point. To achieve as little interaction of the residents with the technology as possible without losses in quality but with considerable comfort gain... in normal operation the residents should actually forget that these things even exist...
And no, an app on the phone does not create a comfort gain but quite the opposite. Because it makes you dependent. Many of these so-called apps are nothing more than a replacement for a usual remote control and still require operation by the residents. Certainly, there are then rudimentary logic functions and automatism on board but they operate according to your own parameters and are always dependent on further data. Or, for heaven’s sake, a constant internet connection for their own cloud. This has absolutely nothing to do with an automated home and is often just a pathetic attempt to imitate what others have long been able to do, with mediocre success.
What bothers me most is the multitude of protocols and the proprietary technology and manufacturer-dependent software.
For this reason, one also leaves this electronic waste aside and goes for open and manufacturer-independent standards.
nowadays Wi-Fi capability and a suitable app, for that I don’t need an elaborate smart home system. For example heating system/heat pump, photovoltaic system, charging station, video intercom system, vacuum cleaner robot, etc.
And here lies the problem. Because that is exactly what you should not do. For many reasons, among others, for example, from the environmental aspect that mentions. Resources are finite and do we really need a Wi-Fi access point at every socket now?
besides the unpleasant feeling that a hacker could get into my house,
You only have to fear that if you also allow it. Granted, with all these simple systems from the bargain bin or the startup around the corner, which rely on an internet connection, there often is no other option than to leave the accesses as wide open as barn doors. But that doesn’t have to be. You don’t have to surrender to the clicky-colorful and data-hungry faction. You can also go for systems that work wonderfully completely autonomously and without unauthorized external access, and indeed manufacturer-independent without being forced to choose one or the other.
but my impression is: automation becomes absurd at a certain point and behind it stands, in my feeling, a misunderstanding of what is beautiful about life.
Absurd is what’s going on out there right now with dozens of protocols and even more products that are hardly compatible with each other. Not to mention that many stick a bunch of boxes onto themselves and acquire plug adapters that do not exactly please the eye and often barely last beyond the warranty period. Here lies the problem. In the waste of resources.