Meanwhile the key is to become proficient at using worktrees to parallelize agents instead of working serially with them

Sounds nice, in theory, but in practice I want to iterate on one, perhaps, two tasks at a time, and keep a good understanding of what the agent is doing, so that I can prevent it from going off the rails, making bad decisions and then building on them even further.

Worktrees and parallel agents do nothing to help me with that. It's just additional cognitive load.