GO FOR IT, NEWBIE!!!

But how do you know that all the magic was there? Maybe there were only 1-2 levels.

There are no Pandora boxes with magic of levels 1-2. They can contain magic of levels 1, 2, 3, 4, or 5, but only separately. Or magic of one element completely. Thus, if, for example, we take a Pandora box with Earth magic of levels 1-2 and a hero without Wisdom, then we can be 100% sure that the rest of the Earth magic was also there. Or, for example, we take an "empty" Pandora box with a hero with advanced Wisdom and who does not have all the spells of levels 1, 2, 3, or 4 in his spellbook - then it can be said with certainty that all level 5 magic was there.

Added 3 minutes later

Still, I think like this:
If a hero does not have a sufficient level of Wisdom to learn spells from the Pandora box, then he can use them with the help of scrolls, but only after building the corresponding Guild. Because (let's take the library principle, there is level 10 - get everything plus 2, otherwise it's impossible), increase your Wisdom...

Pavel and Roman's thinking is at the level of "I think it should be unfair." The fact that the rules say something else doesn't particularly bother them :)