Storing and organizing performance review data - SharePoint lists or something else?

You've been given some really sound advice here! SharePoint lists will technically work for maybe 30-50 people but once you hit a few hundred it becomes really painful. While everyone mentioned the difficulty on the admin side, I also actually want to address this from the performance review aspect. The experience you're describing.

The bigger issue is that employees and managers need a clean, guided experience for reviews. A list view with 15 columns and a bunch of filtered views doesnt feel right for something this sensitive. Since someone already mentioned Entra ID integrated performance platforms, I'll double down on that too. 

I know that Teamflect, Leapsome, and Performyard all have that feature. So all worth looking into. I know Teamflect is best for MS365 but I know the others are also worth checking out.