Essays are often about organizing other's thoughts, from references and other source material, and your own thesis based on that.

Organizing and arguing your own thought would be a good test. I think an assisting tool could still be reasonable - choosing between different organizations. Though it's unclear how to assess for original thought - the only such "essays" I know of are PhD theses.

People said similar about log tables and slide rules. And they were right - something was lost (e.g. the sense of nearby solutions). Yet here we are.