GMforPowergamers
Legend
I don't think that it is unfair to anyone not prof... but I think the prof system of saves is unfair.I'm still waiting to find out if fireball is unfair to characters not proficient in Dex saves.
in 2e (when I started) PHB Ch9 The Saving Throw each class got BETTER at resisting spells but in 5e most classes get worse.
lets take a caster with a 15 in there prime stat... so 8+2+2 for a save so DC 12 (not super good but not super bad)
a character has 6 saves useing the defualt array +2/+1 that gives them lets say 16, 16, 13, 12, 10, and 8 again not perfect but not bad... that next lets put a 16 in a prof save stat and 1 16 in a non prof save stat... but put the 13 in the other prop save stat.. that makes our saves +5 +3 +3 +1 +0 -1
lets advance those two characters to 11th level... and say the one making the saves is a rogue or fighter so 3 stat ups... making it 20 16 14 13 10 8 with prof of +4 and I will give +1 magic to all saves... so +10, +7, +4, +2 +1 +0
over all my saves improved by 5, 4, 1,1 ,1 and 1
now that caster only gets 2 increases... but that can bring them to a 20... lets not give them any magic ups though dc 8+5+4 DC 17 (now that is a good save DC) only 1 save kept pace and the other 5 ALL FELL BEHIND...
so your example of fireball not only needs to be prof but also a stat you are keeping up with the caster to not fall behind.
even prof, with a 13 becoming a 14 and a magic +1 lags 1pt behind between 1st and 11th level.
lets look at 1st-11th level fighters in 2e they start needing to roll above
14 | 16 | 15 | 17 | 17 |
7 | 9 | 8 | 8 | 10 |
an improvment of 7 7 7 9 and 7
even if the wizard gets something (I know there were magic items but I think there were non weapon profs in the dragon mag) that applied a negative they would need it to apply a penalty of 6+ pts and I don't think that was possible,