Old sailfish user here, currently on an iPhone. The following things are why I switched.

• No support for Bluetooth LE, either natively or in the Android emulation. (So no smart watches, bike computers, etc.)
• Bluetooth headphones worked fine. Mostly. And not with any good codecs.
• The native app ecosystem was small. You will need to fallback to android emulation for a lot of things. In particular, good luck getting any commercial apps natively (trains, banks, and so on).
• The native apps that existed were clearly hobby projects, mostly written by one person for the use of that person. Which is fine, but none of the apps I used left enough of an impression for me to remember them.
• The web browser was fine to use, but absolutely not up to standard w.r.t. security (at that time). Plenty of known issues in the underlaying engine.
• No decent native app for maps. I never tried a native app that managed over 15fps when scrolling around. I think I also had issues with position data in android apps…
• Finally, I was constantly switching between two very different user experienced - emulated android and native sailfish.

Native sailfish was absolutely wonderful. It worked flawlessly when I stayed within the fearures that were available natively. But in modern society you simply can’t get away without all the android/ios stuff. At least not unless you have a lot of time and energy to fight the system, and I currently don’t have that.

This was a few years ago, so things may have changed for the better. I’ve been busy and haven’t kept track.

But if you want something to do - write an amazing maps app for native sailfish or get the Bluetooth LE-stuff working.