I’m probably risking a lot of downvotes with this one, but for me it was a Home Assistant setup. Not really a purchase because it’s an open project, but I invested a lot of time into reading the docs and setting it all up only to realize I didn’t actually like it better than using the smart home products directly. It seems like a great option for people who like to tinker and get a thrill out of getting some cheap Aliexpress gadget or ESP32 project to work with their home, but I just wanted something simple that worked for my house without extra complexity.