That seems like an empirical question. I can see that it could be true of toast, but it certainly depends on how simple the input is. It's not easier to make a cake myself than it is to tell a chef how I like my cake and let him make it.
If your interaction with your toaster is that it asks you "How do you like your toast?" And you answer "lightly toasted", by speaking, that seems pretty easy, just as easy as adjusting a knob to "lightly toasted". It can then refine it's toasting based on subconscious reactions, facial expressions, etc, just as a human could. It could then try subtle (so as to avoid too large a change in the wrong direction) trial and error with feedback from those cues to improve it's toasting. It might add to this a model based not just on your behaviour but on observations of other people made by other toasters.
Of course, this is assuming some future much more advanced AI than is currently available, but I'm pretty sure that's what we're talking about.
You know you've described something that already exists and is crap, right?
Because you only need to look at Google's YouTube recommendations, to see how exactly what you describe goes horribly wrong. Because at some point Google quite conspicuously stopped giving a flying f-bomb about actually doing anything for the users, and just started using several of its services as testing grounds for its algorithms. Including stuff like giving everyone the same set of images of streetlights and street-side stairs in its captchas for a few weeks at one point, presumably because it was training its self-driving car AI, and who cares if it defeats the whole purpose of why a user might want to use a captcha.
Well, based on observing my behaviour and what it thought were clues from it, over the time it produced pretty much only the worst recommendations possible. E.g.,
- it kept recommending Turkish soap operas for years, until I switched my country from Germany to UK. Presumably because, yeah, there a lot more Turkish immigrants in Germany.
- it keeps recommending news -- granted, now about Brexit -- no matter how often I click the X in the corner to remove that. Presumably because, yeah, it looks at what other people are watching.
- it kept recommending wrestling videos for weeks, because ONCE I clicked on one video of Jeff Dunham doing a comedy show for the troops in an event that also featured a wrestling match. In fact, it's become an entertainment of its own to watch the recommendations go retarded if someone sends me a link to youtube.
- it can't seem to distinguish between playlists that are supposed to be watched in a sequence, like a TV series or a game Let's Play, and a random music list. Or at least I assume that's what happens when I watched episodes 0 to 9 of a Let's Play in order, and then it recommends that I watch one of episodes 19, 21, 13, 17, 8 again, or 12. Presumably because those got the most thumbs up. But conspicuously missing is the only one that actually makes sense to watch next, which is episode 10.
- it keeps recommending only the games I'm not interested in, but presumably the ones that kids these days play the most. Because, hey, they're all tagged as games. If you've watched strategy games before, surely you're interested in some twit bragging about using aim-bots to "pwn noobs" in games like Fortnite.
Etc.
Now all those could be solved MUCH easier by just letting me do the same thing as in Steam, namely let me set some options and tags/people I'm interested in, and ones which I don't. Especially the last one. Other than wanting to keep me as a lab rat in perfecting its learning algorithms, trying to guess what I'm interested instead of just letting me block certain twits, there is literally no advantage in doing the former instead of the latter.
And in fact, not only that, but its guessing game by now screws up even the search, where I can theoretically set some options. But for example, telling it to sort results by upload date is producing hilarious results that jump back and forth by months, while not showing at all more recent videos which I know exist.
And basically that's the problem with playing that kind of guessing game.