Why are some Getting Started steps locked?

Because they need a planting to work with: create your first one and they unlock, in the order that builds your season. Organize My Crop Map, Check My Seed Inventory and Manage My Workload stay grey with a clock until then.

Add a planting with Create My Game Plan, and the three steps open.

Once you know your way around, Dismiss the product discovery steps on the welcome card hides the page. See Your first steps in Heirloom.