From SAP engineers in SAP source back in 2005-ish:

What does this do?

Agile is good for projects that by their nature contain many small objects that can be developed, debugged or even completely rewritten in short time frames. Web page and web site development can be examples.

Waterfall is better suited to projects where there are many large components that need to interface with other large systems, or projects with complex regulatory compliance needs, or complicated business rules. These projects often sit behind waterfall projects, such as data stores, OLTP databases, HR systems, etc.

The problem is that Agile has become the new hot answer to all that ails development, so it is being used where it is inappropriate. It's like trying to use a hot new Tesla for your mass transit route because it is the cool new thing , when you really still need a bus.