First of all, doesn't it give you Advantage on your next "attack roll" - as in, melee, ranged, or spell?
It's as Warlocke above says, with two possible use cases (that are made ~irrelevant in BG3):
1.) Casting a high-level spell that you don't want to waste. However, True Strike requires concentration, which you'll both likely be already using and which has a high likelihood of being lost due to BG3's prevalence of auto-damaging effects. Also, high level spell slots aren't as valuable in BG3 since there are no long rest restrictions.
2.) Using Quicken Spell. In 5e, it might be effective to cast True Strike and then Quicken your spell to cast it as a Bonus Action. However, in BG3 you can just cast the spell itself twice because Quicken doesn't restrict you to casting a cantrip with your main action.
