Mature is one word for it.

Struts does a great job of automating the controller and navigation logic for
Web applications, but some of its older libraries overlap functionality of
newer standards like JSP EL, JSTL and JSF. The Struts project has done a great
job of moving with the changes in its most recent incarnations; its web site
is chock-a-block with advice on how to use these standards in conjunction with
Struts.

Many people ignore this advice and use Struts libraries instead. There are
also ways to use the core Struts framework to engender horrid complexity
should one choose to do so. One could argue that any web app should have
sufficiently straightforward navigation requirements that Struts action
classes need not each dispatch to a zillion different processing stages, but
then some seem to disagree.  Struts is flexible enough to satisfy the most
twisted spaghetti-logic addict.

I suggest using Struts in its leanest pure form, expecially its most recent
incarnation, preferring the newer standards to the older non-core Struts
libraries.

One could also write one's own controller servlet and simple "action" handler
layer. It's not a whole lot of work for most straightforward applications, but
it will help you appreciate Struts's value and how best to use it.

Going back to the original point about developing in the "simplest way": if
you ever think you need to "disable" the browser back button or refresh, you
have seriously lost your path.  Make your transactions idempotent and don't
every try to change browser buttons.  The misguided attempt to suppress
browser navigation idioms introduces amazing difficulties and astounding
schedule slippage to your projects.

The larger principle is that no framework or technology mix will protect you
from having to do correct analysis and modeling, or against the consequences
if you don't. Achieving the "simplest way to develop" depends on an
architectural approach and mindset more than on your tools.

- Lew