[mvkg]

5GHz certainly helps, but congestion/co-channel interference can still be an issue in high density environments, especially in a multi-user environment like an apartment complex where nothing is coordinated. The addition of 6GHz will help alleviate this problem too, but a lot of consumer gear seems to default to the widest channels possible.

Also, your glass door probably has Low-E glass which has a metallic coating.

> The future is probably just having multiple wifi APs wired up and then just running extremely fast but low range wifi.

This is somewhat the case, but it is limited. For example, in 5GHz there are 21x 20MHz channels available. In a highly dense environment, this can support roughly 30x devices per channel well and 50x devices per channel with some degradation.

Limiting the TX power on an AP can help, but it's not a panacea since clients always transmit their control frames at their default power (usually ~15dBm). There have been some improvements to this in .11ax, but depending on the spatial organization of the devices, it can only do so much.