It's actually a much more interesting question than you might expect. Lots of modern appliances could run perfectly on DC of around the RMS voltage. For example

It's actually a much more interesting question than you might expect. Lots of modern appliances could run perfectly on DC of around the RMS voltage. For example the most modern fridges rectify the incoming mains to drive a brushless DC motor, this allows them to run at an appropriate speed rather than using bang bang control. Even an an induction hob, you might think it was most reliant on having an AC waveform but actually they need a much higher frequency so again they rectify the incoming mains. Obviously it's not quite that easy, for example an oven uses resistive heating elements which would work fine on DC, however, the relay in the control circuitry wouldn't be able to switch a DC voltage.