Slowing the game down and reducing the damage done by bosses isn't rocket science. It's like ten lines of code, which have been written so many times an AI can probably provide them.
Different people have different capacities to engage with a game. The world is a better place with some simple accessibility concessions.
We don't need to make excuses for game developers who don't even do the minimum, unless it's their first game.
Edit: To me, the "Watch a playthrough" argument misses something fundamental about why people choose games over movies.