A schema isn’t only for performance, but also for constraints. In Neo4j, people often add redundant data for performance, for example if you often need the number of nodes up to 3 hops away, or they want a certain type of link not to have cycles, but there’s little to no help from the system in keeping those constraints.

Whenever I hear the claim any “noSQL” store is so much simpler than a SQL database, I mention performance (efficient storage and querying) and constraints and then say “give it 50 years”.