Leatherhead
Possibly a Idiot.
Huh. Do you think that's true of Faerun? I mean, maybe it's in the "lore" (I really don't know...I've never found FR lore to be interesting enough to dive into) but I don't see signs of it in the adventures. Where are the indications that today's wizards (with 9th level spells, including Wish) are less powerful than wizards of old?
Wizards on Toril could cast up to 11th-level spells before the fall of Netheril (which was caused by the casting of the only 12th-level spell ever)
Also the Netherese had flying cities (yes, multiple), and magical toys for all the children (think like an ipad, but better). Their magic was so magic, that they changed the rules of how magic worked in controlled areas. When featured in an adventure, the central plot point devolves into not letting people use the Netheril magic because it is too world-breaking.