Observability stacks, while effective in monitoring technical aspects like metrics and logs, are not sufficient to capture the full scope of user experiences. Users engage with applications in diverse, unpredictable ways, often outside the parameters that observability tools can detect. Human customer feedback fills this gap by offering real-time insights into how users interact with products and where pain points lie. 

By combining observability data with customer feedback, companies can gain a comprehensive understanding of product quality and make more informed decisions to enhance user experience and satisfaction.