I get the idea behind this article, but the process of estimating a project is more complicated than what can be solved by your proposal.
First of all, you have to think about *when* the estimate is needed. If your company does software for a living, then you won’t have a team ready to estimate every single proposal you put out there. My company sends 5 proposals every week, so it is impossible to estimate the work using the same people that will implement it.
Second, estimates at this time (when putting together an initial proposal) are done at a much higher level than what you describe, but they are still estimates. The outcome of a proposal will be a specific budget and timeline.
When a proposal is approved, you have to work within those constraints. Estimating the work afterward is still important (here you’ll focus on a task at a lower level). This is not wasting resources, is just doing a different type of estimates.
Finally, the premise that Agile makes the assumption that deadlines aren’t important is completely false. Why do you think that’s the case?