Yes but that’s expensive and only part of newer WiFi standards, and almost nothing implements it. Most devices barely even support basic MIMO.
The point remains that I won’t go replace lightbulbs just so they run 5 GHz WiFi. It’s dumb and pointless and just generates a ton of completely unnecessary and avoidable ewaste, just to avoid using a network band nobody cares about anymore.
In an ideal world yes, everything would be 11ax already on 6GHz spectrum. But this is the real world, a world where 10-20 year old WiFi devices still connect to 2.4 GHz networks and are still useful and most importantly, still works perfectly fine. WiFi 11n chips are dirt cheap, why should we have to add an extra 5-10 bucks on a lightbulb just so it’s on a modern WiFi standard when all it needs to receive is an RGBA value to know what color and how bright it should be. At that point it’s an economics problem not a tech problem. Those devices couldn’t even handle maxing out 11n even if they wanted to anyway, they barely handle a web server.