The fun doesn't stop once you have reached Level 50 in Diablo 4, as this is when part of the endgame really starts. At this level, you unlock the Paragon Board, a whole new screen separate from your Ability screen you've been working with that allows you to get even further into the nitty-gritty details of your build.
Diablo 4: Paragon Board Guide
Diablo 4's Paragon Board offers a ton of customization for players after max level, but it can be overwhelming without guidance.