there are so many problems.
in standard 5e firebolt and sacret flame are similar in power-level. both have an about 60% hit chance on average. 1d10 vs 1d8. sacret flame can target enemies behind cover.
in bg3: firbolt 90% chance to hit. high ground advantage. lights ground on fire even on a miss. does 1d6+3d4 dmg. explodes barrels. lights grease on fire.
and since goblins have 15 hp instead of 7 even if your 50% sacret flame hits it doesn't even have a chance to kill!
same with aoe damage. be it shatter or fireball. if enemies have double the hp these spells just suck.
as for eating a "whole chicken" as a bonus action. yes you can do that. i think i have played 3/4 of everything there is to see in act 1 and i have hundreds of food items in my inventory.
why give fighters second wind when i can just eat a pigs head every turn.
also healing spells are irrelevant since they were weak in combat to begin with and everybody can heal a downed pc and that was the only thing healing was really good for.
Sacred flame is kinda underpowered not because of its damage, but because it requires a dex save, Most enemies are pretty decent in dex usually a +2 for save so thats a what 12 of 20? That is 60% to hit which is...oh yeah the number you see for most of the game.
Fighters having a free heal is fine because most foods will not heal that high, and if they do, they are limited and heavy.
SOME of you are saying that spells are weak because they dont one shot enemies. That is terrible thinking besides, fireball is going to do 8d6 damage (21 avg which is high enough for most goblins, minus a few lvl 3 ones and will at least bring them to almost death which they will die if the fire pool under them gets them)
Firebolt is 1d6 + 1d4 from ground. Plus 1d4 if they continue to stand in it and take another tick of fire dmg. And its not always a 90% chance to hit, firebolt is a spell attack based on the % AC, height, light etc...
in 5e anyone can heal a downed pc, The only difference is that BG3 aid brings them to 1 hp, where as 5e stabilizes and gains 1 hp every 1d4 hours..
Compared to 5e are casters underpowered no. What is underpowered is the idea that some people expect to kill certain enemies faster simply because they are "supposed" to have x health based on their mm sheet. The dm can change that, and this DM has.