The Grand National will end, it does every year. It's only on for ten minutes or so. If you don't like it, don't watch it. Sure in the old days there were only a few other channels but these days there is a much bigger choice or you can just stream something.
Anyway, I don't get the cruelty argument. They're horses, you can't make a horse run if it doesn't want to. Horses often refuse to start a race because they're not in the mood. With a big race like the Grand National, they're some of the best horses around - they have to have had a few decent runs in the past to qualify for it, so horses that hate racing won't even get into the field.
What irritates me is the so-called "safety" changes that have been made for this year. They actually make the race more dangerous. Personally I think the risk is acceptable but it is illogical to make a race more dangerous than it was in previous years in the name of safety. Reducing runners, reducing the run in, a standing start, all this means is that the first few fences will be more even. Less field spread means a higher chance of interference, collisions, fallers and fatalities.
Don't get me wrong, nobody wants to see dead horses with a tarpaulin thrown over them as the leaders progress through the second lap (indeed we probably won't because the cameramen and director are more aware of the bad optics), but the safety changes for this year make the race more risky in my view.