Are you treating everyone in your organization as equivalent resources or are you allocating people based on strengths/specialties?

Having a heterogeneous team with breadth of experience across the stack helps to isolate you from the real business risks of group-think and "not knowing what you don't know". It's a hedge and a pillar of a resilient, long-term-oriented organization.

If you just want to have a get-shit-done culture, move fast and pivot/abort when things get bad, you probably want all 20 year olds. However, if you look at the organizational structure of banks, who are literally in the business of managing business risk, you will see diversity and redundancy in hiring.

Side note: Every single time I've seen a complaint about X group doesn't work as effectively as Y group, it's almost always a management misallocation of (human) resource. Not calling you out specifically, just wondering how much thought was put into team/work structure.