Can you make even a single example of "build planning" in Baldur's Gate that goes deeper than "I'm gonna select this race and this class"? I guess you can select your weapon, but that can be considered "build planning" only if you are mentally impaired.
It still allows you to make 1 HP mage, specialize in weapon that barely exist in the game or make warrior who is unable to wear a metal armor due to its weight.
You know you can do all that even with D&D 5, right?
You can create a Wizard with 3 in Constitution, so that you start with 2 hit points on level 1 and barely gain any additional hit points levelling up. Having 20 hit points at level 20 is exactly like having 1.
You can specialize in a weapon that barely exists: you just need to use that weapon. Since it's a "flavor" thing that doesn't impact rules, your weapon of choice can be anything.
You can make a warrior who is unable to wear a metal armor due to its weight: you just need to make a warrior who's Strength score doesn't allow him to wear heavy armors.