How do you establish authority as a technical lead when managing resistant senior employees?

Posted by RNNDOM@reddit | ExperiencedDevs | View on Reddit | 91 comments

I've been brought in to modernize and upskill a team of 4 developers (including myself) who've been with the company for 10+ years. While they have significant tenure, they lack formal IT training and modern development practices (git, CI/CD, Scrum). A key part of my mandate is ensuring the team follows the product roadmap - historically, they've worked on whatever they pleased without accountability, resulting in consistently missed deadlines.

Management wants improvement but replacing team members isn't an option due to labor laws and company culture. While one team member is supportive of the changes, two others are actively resistant. Recently, they excluded me from a critical incident that took them 2 days to diagnose unsuccessfully (which I diagnosed in 5 minutes when I finally found out).

How can I assert my technical authority and implement necessary changes while maintaining positive relationships with these resistant team members? What strategies have worked for others in similar situations?