I think I would have to say washer, dryers and microwaves hands down. Basically anything that requires you physically present to use anyway. You gain almost no new functionality with them being smart, and you don't even get the ability to be lazy with it. Locking functionality behind an app doesn't make sense in this case and just dampens the user experience.

That being said, I think many "smart" household appliances could be better than the non-smart appliances if it didn't cause them to function like shit. Like I love the concept of asking my fridge from the store what's in it and getting a reply, it's just companies don't give a shit what the consumer wants (see samsung putting full screen ads on the panels) and only do what is the least amount of effort to allow shoving telemetry and ads. That's all they really care about, a new revenue front.

Being said, I doubt I'm the expected audience for the question, my smart devices I use daily would be my watch which is great for fitness tracking, smart bulbs which let me auto off the primary lighting in the house when I go to bed including downstairs if I forget, a smart plug that disables my heater downstairs if I forget to shut it off, and a smart thermostat (which isn't allowed to connect to the outside world). And a garage door which I love getting notices if it gets opened for because it's nice for security. All stuff I could live without but make my life easier.