Both their functionings are complex, so people can get impressed. But for both of them, all the complexity is inside the device and there isn’t much to put together; and the way they hook up to your house is really simple.
Why YSK: so you don’t live too long with a broken toilet or garbage disposal, thinking it will be too hard to replace. Those two are some of the simplest things to DIY.
I would disagree that taps are easier, I replaced taps before, and not only are P-traps pretty hard to put together, but it can also be kinda tough reaching to the connections under there.
But I take your point that I’m an able-bodied person able to carry the toilet off and another toilet on. If anyone is not, then yeah they’re pretty nasty to lift, so you might want to call a professional indeed if only just for that.
I have a siphonic toilet and it wasn’t particularly splashy, but I did sponge all the inside water out before taking it off. I can imagine that it would have been a mess if I hadn’t.