Planning a dimmer - still relevant?

Actually, one should take the path away from manufacturer-specific switches and dimmers and instead use universal ones where it doesn’t matter what kind of lamp is connected in the end. These switches (more like push buttons) can be dumb, semi-dumb, or intelligent, as Untergasse mentioned.

The dimmer is then often located in the modern electrical system in the distribution box or at the lamp. It also doesn’t matter where it is operated from.

Alexa can be supportive or just another operating option. By no means the main or the only one.

To answer the initial question, yes, dimmers are more than relevant and are becoming increasingly relevant and functional, just not in the rigidly wired rotary variant.

If you choose a classic electrical installation - but want to keep a few options open for certain areas of the house for future changes - then you could, for example, connect some push-buttons/switches/dimmers to the lights via the "detour" through the electrical distribution board. This preserves one or another option for changes, for example, to install dimmers/other control elements centrally in the sub-distribution later if necessary.

However, such options quickly add some extra effort. For 12V/24V systems (e.g. LED strips), larger cable cross-sections to the lights are sometimes helpful (with the transformer in the electrical distribution), possibly also shielded cables and additional cables for sensors. In the end, everyone must individually decide which option makes sense for them.

In case of doubt, a few extra cables in the walls always help reliably to ease the conscience in the here and now.