Even without modern things like ground fault interrupts and fuses it would be pretty hard to actually get a shock you would die from in a bathtub. Water by itself isn't actually that conductive, it's the impurities that conduct the electricity. Now you could argue that a bath a person has sat in probably has a lot of salts from the body and maybe some kind of bath soap with a lot of salt in it. But still it will be hard to get an electric shock enough to kill. Usually when someone dies from electric shock, it's because the heart gets interrupted and doesn't resume the normal function. The brain dies from lack of oxygen. In a bathtub the normal flow of electricity would be from the toaster to the drain which is normally earthed, either directly (modern installation) or indirectly (old installation). There would be no reason for the electricity to go trough the body, as the body is at the same electric potential as the rest of the water. Let's assume the water isn't grounded in any way, a fully plastic tub without an earthed drain or taps. Then the most direct path for the electricity is to go from the hot line to the neutral line. This will probably mostly go trough the heating element, but a part will also go through the salty water. The water in between the two sides of the toaster will get heating and may even boil, plus the heating element will degrade due to the reaction, but outside the toaster the water won't be affected much or at all. The hot water would be more dangerous than the electricity. If the person were to be close to the hot and neutral sides of the toaster at the same time, maybe it would be enough to kill? Most likely it would be enough to cramp up the muscles in the arms, but probably not enough to stop a heart.

I'm not saying it's impossible, but it would be pretty hard.

Plus we've all seen the BigClive vids where he puts his hands in salty water with electric mains in it.