WiFi 6 -> 5 compatibility mode – how often is this needed in practice?

I am about to buy access points and have now read about the “Compatibility Mode”.
Since some (very few?) older clients are said to have problems with WiFi 6, this mode downgrades the entire (!) network to WiFi 5.

Now I’m unsure whether I shouldn’t skip WiFi 6 and instead use better (more antennas/streams….) WiFi 5 hardware.

To what extent is this really an issue in practice?
Or is that usually hardly a thing and only affects very exotic older hardware?

Thanks and greetings,
Martin