IMHO, it would level the playing field for honest manufacturers and service providers.
Sure, it would effectively outlaw many types of ads that we see today, but do you think any of the types of ads that rely on hidden fine print are really all that valuable to our economy or society?
Let's take guarantees and warranties. There's certainly nuances there. Should all those also be disclosed in the main copy?
Let's take the main thing here. What if they went out of business? Forever never actually means for perpetuity.
All these are obvious? So is the rule to stare everything but the obvious? Who determines that?
There's so many practical details that complicate things here
In fact, much of these things have made their way into the law a long time ago. Maybe you just want to restrict the freedom of how they can display it?