Since Apple hasn't updated the Airport Extreme in a while and it looks like they will never update it considering they disbanded the team that was working on it, is it still worth buying? Is there a better alternative?
For my home office, I wanted a new router that is stupid easy to use but with more power options that also wouldn't be abandoned. I ended up with a Synology RT2600ac after reading Tweaktown and seeing the video review by 9to5Mac. I've installed and am using some of the firmware packages - the VPN Plus server, the cloud backup (and desktop apps). Bought it from Amazon for $225. Attached a 8TB WD easystore (with a WD Red HD inside) and installed a 64GB SD card so they're local storage spaces I can access out while out on the road. Mac and iOS apps do the job. I'm happy with it.
You ought to take a little time and investigate the various "mesh type" systems that are now on the market, such as (but not limited to):
- google wifi
- eero
- Linksys Velop
- Netgear Orbi
- Ubiquiti "Amplifi"
A good place to start is by reading the amazon reviews (YouTube, also).
I wouldn't buy an Airport Extreme now, for the reasons you mentioned above.