At least some of the remarks here show a very poor understanding of what cabin crew are and what they do.
No, pilots cannot replace cabin crew without substantial formal training.
Cabin crew are highly trained professionals, just like pilots. It's true that unlike pilots they are not in command of the machinery, and that their role requires them to do many much less glamorous, high-prestige tasks than pilots have to do.
That doesn't make them any less professional or trained. Instead, they manage people in large numbers and their behaviour and look after their needs, in an environment that is both unnatural and stressful, and tends to provoke poor behaviour.
Amongst other things, they typically speak multiple languages, have first-aid skills and can deal equally effectively with a weeping widower, a gang of drunken oil-rig workers returning, someone having a panic attack, an over-entitled business executive, etc etc etc.
In cases of emergency, they are responsible for ensuring the safety of dozens or hundreds of frightened people, by getting them to stay calm and follow instructions.
Anyone who imagines that the people with these skills and training could effectively be replaced with people lacking them is dreaming.