I don't think it's a matter of making process for the weakest engineers. It's more likely that we're trying to apply one monolithic process to highly variable work.
You hit on something super important that I don't see discussed often enough: Different phases in the software lifecycle require different approaches. Trying to apply "maintenance mode" to a greenfield project (or vice-versa) can be a disaster for the reason you mentioned - sometimes you just can't break the job into small changes until you have something concrete to change! There is time for principled slow change, and there is a time for rapid prototyping. But most teams use a single process for both.
You hit on something super important that I don't see discussed often enough: Different phases in the software lifecycle require different approaches. Trying to apply "maintenance mode" to a greenfield project (or vice-versa) can be a disaster for the reason you mentioned - sometimes you just can't break the job into small changes until you have something concrete to change! There is time for principled slow change, and there is a time for rapid prototyping. But most teams use a single process for both.