Obsessive levels of memorization. I can't remember my best friends birthday but I know the area of effect of faerie fire 🤷‍♂️

5e is pretty simple, spreadsheets were needed for Pathfinder 1e and 3/3.5. Multiple attacks around, each at a different to hit modifier, then different modifiers depending if you were using different feats. It was beautiful chaos.

The answer isn't usually on your character sheet. But I play other TTRPG's. DnD is basically a fighting simulator where people go to tell stories.

The More Purple More Better character sheet does all that for me ;)

It can be done, but spreadsheets are fun too. ; )