I was an Apollo user when I had an iPhone, then moved to Android and was a Boost user to finally move to Sync, now all of these 3 are dead, do you really think I'd want to keep being active on that "community"?
These devs deserved better, luckily both Android devs moved here, and they will receive the support of their followers, and Apollo already has numerous spiritual successors, Wefwef/Voyager being an awesome PWA and some iOS apps like Memmy and Artemis!
I really liked boost on Reddit, but it probably comes to personal preference. Haven't tried anything else (besides the official app years ago) and never felt the need to try anything else.
I was converted to Reddit by RiF but when I discorvered Sync I jumped ship because it has the best scrolling performance on my shitty Android phone at the time.
Boost is great, but I've had more success replicating the old.reddit experience using Sync; the compact/list view feels more "right" to me. I originally started using it because it was the closest analog to Alien Blue at the time, and I never saw a reason to switch. Damn, I used it for almost 10 years!