They're not, but the way we're filling our time while waiting for LLMs involves much more context switching than how it was with tools and human bottlenecks like manual coding. I think it's fine to work on two or three things at once, provided we don't let the LLMs decide when we should tend to which task.

You now have a “manager” schedule not a “maker” schedule. [1]

The agents are the makers; you switch among them. Either that or watch grass grow.

[1] https://www.paulgraham.com/makersschedule.html