I have pretty much always used spells as written in 5E, but now that I'm back after a long absence I've rediscovered many of the 'liberties' that Larian took, and they are making me increasingly frustrated (I avoid using them, but the enemey AI sure doesn't).

Take acid: any effect that creates acid - flask, spell etc - reduces your AC2 by 2...given how critical each point of AC is in 5E, this is pretty unreasonbale, esp for a low level item/ability. It is completely a home-brew rule. As is the creating of acid/effect patches for spells like chromatic orb - there is no AoE for these in 5E - this hugely increases the spell's power and versatility. It is designed to affect 1 target only: adding an AoE /persistent effect is the equivalent of a higher level spell. Also, creating patches means that you can hit allies now, with a spell that is designed to effect one target only.

I know some like these 'fun' additions, but for the love of all that is holy/unholy can we please have a core 5E setting?

This kind of stuff has already made BG3 drop in my esteem - it is gimmicky and dimisses years of experience and tunnng by the D&D developers/community.