I feel like there are massive industries that exist just because of this

Everyone uses about 5% of the features of their word processors, but it is a different subset for everyone so all features are needed by someone and most get equal useage.

I do not think that is true. There are definitely more and less commonly used features. Everyone uses basic formatting, but only a small minority of users use index or bibliography features. The features might matter a lot to that small minority, but they are not anything like equally used.

There are a small minority that everyone uses. It quickly falls off.

Ehh the issue is features tacked on w/out regards to existing ones. Lotta apps like that end up with multiple ways to do the exact same thing but with very slightly different use cases