What dont you understand about "cant string together spells anymore"? I didnt say WHY they were an ex-archmage. Experiencing an enjoyable story > winning a squabble with goblins. You make no sense at all, you have some weird hatred towards anyone who doesnt conform to your standards, if that player with low stats portrays an interesting character then no sane person gives a crap about whether or not they have good stats, since for the 100th time that is not the purpose of DnD. If you NEED that wizard to have perfect stats in order to win every fight then you have set up a very restrictive campaign and are not a creative DM