Many people think that waterfall is the only way to work, and they don't understand what is agile.

In waterfall development, a business analyst gathered requirements well in advance, then they created a feature from those, adding detail after detail until they got something they could estimate.

They (or a manager) put them onto a Gantt chart, and threw them over the wall to the programmers, who build exactly what was presented to them, then threw it over the wall to QA. A team-level Project Manager kept them on schedule with regular reports and meetings.

How is that different from what many so-called "Agile" teams do, though they use Jira and a backlog instead of Gantt charts and pretend that the requirements are "stories"?

Agile is a radically different way of working that bears essentially no resemblance to what I've just described. If what you're doing looks like that, my suggestion is to look long and hard at how you work.