What systems do you consider must-have for well-rounded TTRPG literacy

I'm currently DMing a DND campaign. However I try to be more well-rounded and DnD for me has some flaws mechanically speaking.

I try to expand my TTRPG collection to get more familiarity with systems and maybe convince players once we done in a year or two to try something new. For now I bought WFRP & Imperium Maledictum for nostalgia sake. I though about extending collection slowly to something from World of Darkness, Cult of Cthulu and maybe Cyberpunk but I would like to ask what the community thinks first.