Agile is not about improving performance - its about removing the burden of efficiency proof from management. Pre-agile every manager had to be constantly on the prowl to get "numbers" and dates from teams, to gain a metric, to show progress, to demonstrate them actually having a place and job in the whole cooperate process.
Now they can point at realized features and make a funny progress bar from ice-box to Tested.
That this progress bar might hide tech-debt, that some realized modules might have to be silently rewritten to accommodate follow up stories- and thus that one last feature might be as expensive as all that have gone before.
Well that is treacherous developers, slacking off.
It also trades strong global deadlines of the "your project must be done by X" type for weak local deadlines of the "this feature should be done by X" type. That is custom-made for projects that face scope creep.
But, yes, it's impossible for developers to create an overall plan, or for the developers to decide to pay back technical debit. But can still be done by the client, but those normally don't.
Now they can point at realized features and make a funny progress bar from ice-box to Tested. That this progress bar might hide tech-debt, that some realized modules might have to be silently rewritten to accommodate follow up stories- and thus that one last feature might be as expensive as all that have gone before. Well that is treacherous developers, slacking off.