Hardware

The present reliability issues come from the ubiquity of WiFi networks, especially residential. If you live in an apartment building you're surrounded by them, and they're all trying to use the same limited radio bands. It wasn't such an issue when the first WiFi standards were designed.

802.11bn is trying to implement some better interference-dodging and de-conflicting, but it requires changes at the hardware level. Without reading the full spec, my guess is that the WiFi device has to do more active listening to other networks in the area and adjust its own transmissions to work around them - maybe even talk to other devices at the protocol level and do some traffic policing (e.g. you go then I go then you go then I go...) to reduce interference.

I see about 150 wireless networks from my home the last time I scanned, and I don’t live in a high density area. The sheer volume of traffic makes it hard to be reliable. Wifi 6 and 7 brought some improvements (on paper; I still use AC) but evidently there’s room for improvement.

Ethernet cables still reign.

In my area, a good homeplug setup reigns over wifi for streaming.