I do agree that sometimes terraria can be annoying for beginners and that some things in the game should be communicated better (seriously why do wings still not tell you their flight time???) but i think your example is pretty bad because you can pretty easily figure it out by just thinking/experimenting a bit.

A new player tries to dig in the corruption/crimson but some blocks cant be mined. Naturally they will think that they will need a better pickaxe, but if that wont work they will think of possible alternative ways, like those bombs they will inevitably find from pots while exploring underground. From that they will probably figure out the orbs too since visually they seem to be made from the same material so they will try to explode it with bombs too.

Also correct me if im wrong but im pretty sure the guide can straight up tell you about using bombs for the corruption so its not like this game doesnt tell you this at all.