SQL databases provide ACID: Atomicity, Consistency, Isolation, Durability. Transactions are all-or-nothing.
NoSQL often provides BASE: Basically Available, Soft state, Eventually consistent. The system prioritizes availability. Data becomes consistent over time, not immediately.
This isn't worse, just different. If you're counting likes on a post, eventual consistency is fine. If you're transferring money, you need ACID. Choose based on your requirements.