Youre right about this. My Expresses are used only for airplay, so the WiFi mode is either off, or set to “join a wifi network,” depending on their proximity to an ethernet switch. They are basically acting like any other device on a wifi network, and not as a router.

I have three of the latest/last Airport Extreme towers, and two of those are the only ones with the wifi turned on to “Extend a network.” Since they are all on ac, theoretically there should be no slowdown to n speeds.

2019 was the last update… a full year after they discontinued it. They agreed to support it for five years, which would end this year.

I still run my house on three of the last airport base stations placed around the house like a mesh network, and airport express scattered around the house for iTunes.