Pulling a wild bait and switch like that is also a death sentence for a movie. The parent could easily watch or read a review.

I was a kid before the video game rating system came out. Mom wouldn't let me buy Mortal Kombat.

When Popeye entered the public domain, a slasher horror movie was made on the IP.

Sure - Parents should pay attention and the trailers would make it obvious.

However - under your regime, there is no loss to such movies. They get some extra views from an audience segment they weren’t targeting at all.

Replicate this case ad infinitum - people should check and review a multitude of things. Medicines, cosmetics, food, contracts, games etc.

Firms use this as a way to offset risk onto the purchaser.

I hope we can both agree - that the burden of review of regular folk is now impossible.