Well, I both agree and disagree with the points made in the above post.This is a huge can of worms.
1. I've heard other people report the Airport is slow, but that's never been my personal experience with it.
2. While I was trying figure out what was going on with Asus and my smart lights, I was considering shutting off the 2.4Ghz radio in the Asus and using the Airport as the AP for that band, as well as a gigabit switch.
3. It really depends on the person and the environment as to how critical internet being out is.
4. I've only had 1 bedroom and a Studio apartment to judge coverage in, so large houses don't apply to me currently when judging range. With this said both the AirPort Extreme routers I've owned have had good coverage and speed for the environment they were used in.
5. As far as recycling the Airport, I've considered that, but at the same time, I'd hate losing it just because (as an Apple user), and really for the wireless industry the Airport really revolutionized wireless networking as we know it today, so in some aspects it's a collector's item.
Either way, the RT-AX86U, seems to be stable now, and if I were going to pick a backup router, the Airport would probably be the safest just because of the differences in firmware, and even though it hasn't be updated in a couple years, not having a typical web interface, or typical type of firmware probably excludes it from many of the issues typical routers with outdated firmware would run into.