[HereBeBeasties]

Have a look at https://fibery.io

You might be able to build your perfect todo app with it.

Don't like workflows? Don't add a workflow field.

Just you and no team? Don't add an assignees field, etc.

Want unlimited nesting? Set up a relationship that lets you do that.

Need recurring tasks? Set up an automation that reopens or clones tasks with a recurring field you've added, every week or day or whatever.

Want to know which tasks are "available"? Set up a formula field for that which looks at start date, the task statuses of any blockers, and whatever else you like (time of day even).

It's very cool.