When roles such as team leads tell team members what to do, team members are robbed of their ability to self-manage and come up with the best creative solution.
The duty of an agile leader is servant leadership: not to control and coordinate others, but to facilitate their progress and encourage self-management. For servant leadership this is an ongoing and involved activity.
In Scrum, no one Team member would be responsible for “leading” the entire teams work, even in one area. The team is self-organising without sub-roles such as team lead, technical lead, or UI expert. Responsibility is not inferred by any specialisms a team member may have ... the Scrum Guide makes it clear that there are no exceptions to this rule.