The IIBA webinar presented by LN Mishra focuses on the challenges of gathering critical non-functional requirements (NFRs) and the significant impact of missing these requirements on software projects, particularly in agile environments. Critical requirements can lead to project cancellation, and stakeholders often overlook them due to short-term goals or lack of understanding. Best practices suggested include making stakeholders aware of NFR implications, designing flexible alternatives, and creating comprehensive requirements templates and checklists.