For wildlife gardens with native plants, leaving the stems is best practice if not in a fire prone area. From the National Wildlife Federation:

Leave seed heads and flower stalks. Like fallen leaves, the stems and seed heads of perennials can be essential habitat for insects—especially some overwintering native bees—long after flowers have faded, says Mizejewski. Come spring, “cut the stems down to 10 or 12 inches, and native bees will nest inside.” If you prune back shrubs such as forsythia or blackberry, whose stems have hollow or pithy cores, bundle those on your property for more bee nesting sites, says Cane. Mizejewski points to an added bonus of saving seed heads until spring: “They will attract goldfinches, chickadees and other songbirds you can enjoy watching all winter.”

There is nothing that stands out to me as unmaintained, only not maintained in the way people are used to. During spring cleanup and throughout the growing season, invasive species can be removed (and many tend to stick out in the winter as well).