Baldur's Gate spellcasting last something like 3 or 4 sec maximum. (Words)
That's not a problem if it's interresting to see...
But in DoS (and in BG3) everything is cut in two sequences : first when you click the spell, second when you click the target. That mean you'll never see the whole spellcasting in one time. You can't cut a setence of 3 sec in two times, it will look ridiculous.
There are solutions, but they won't change anything and we'll only have a word by spell, which is very sad.
Just think about a cool spellcasting animation/sounds that suits something like this sentence and it's not a problem even in a TB game.
https://youtu.be/kRazxdSCH_0