Embedded code is also simpler because it has to be. When you are confined to a microcontroller, there isn't room for bloated app frameworks, hundreds of NPM packages, etc.

Depends on whether there's room in the budget to integrate something like a full-fat Raspberry Pi board, at which point, your light switches and thermostats can be full-fledged Kubernetes nodes if you like.

Never underestimate software developers' ability to simultaneously over- and underengineer a solution, especially if the only limitation is hardware cost (read: somebody else's problem).