No advice is plausible for people in all situations. For example, if you work at a job and have nobody reporting to you, delegating is impossible.

On the other hand, if you have direct reports or if you're self-employed, delegating or contracting out some of your tasks makes sense *as soon as you can afford it*.

What this lets you do is to concentrate on your highest-value tasks. For example, if you're a writer, writing is what brings in your revenue, so it's what you should concentrate on. Things like doing your taxes are probably not your top skill, so you can save more of your time to write more and bring in more than you'd spend on a CPA to prepare your returns.

Once you're ready to scale up, you can hire others to write, while you manage the business and bring in new work.

Similar things are true for other examples you disagree with.