The ridiculously low number of features offered within HomeKit. Amazon is kicking their Apple core hole in the home automation market.
What is it that Amazon offers that HomeKit doesn't?
I bought in on the Google ecosystem because of comments like this, used it for a couple years and then gave up because of the lack of functionality. I ended up going to HomeKit and haven't looked back, I got a Starling Home hub to make use of my existing Google hardware, set up HomeBridge to bring in everything else and have been pretty happy to be honest. I'm always on the edge of setting up Home Assistant but just haven't found the need yet.
If the features of HomeKit are ridiculously low, what am I missing out on by not using Amazing's ecosystem?