I often forget to take clothes out of the dryer in the garage, so I'm working on an automation to flash the lights by my desk with increasing urgency the longer clothes are left in.
I'm very surprised how well Home Assistant works for its kind of hobby project, it's matured quite a bit from when I looked into it a few years back. It's not a huge win if all your devices are already HomeKit and programmable via Shortcuts, but it's that it can bridge my non-Homekit Nest, ECOVACS, and GE devices into HomeKit land, and offer unified WebSocket & REST APIs to program against.
I can see why companies would send the takedown notices if their API service implementation is low quality. The HomeAssistant user has to be a super-expert, the sort of person to set up a Google Cloud project to create OAuth credentials so you can connect your calendar. There can't be a lot of those people, and the integrations are probably quite spammy with API polling.