“Overgrown” means that a plant is bigger than someone thinks it should be. Like “weed”, it is a completely subjective term. Objectively, plants do not get bigger than nature intended them to be. A plant that is growing enthusiastically is a healthy, happy plant.
Getting bigger than nature intended does happen to people. We call that obesity. Though the obesity rate in the US is now 35%, many of those who are not obese mistakenly believe they are. Persistent exposure to images of supermodels has caused us to mistake malnourishment for a healthy weight, and to see a healthy size as obesity.
Similarly, persistent exposure to lawns has caused us to see a system in which grass is no more than an inch or two tall, and shrubs grow in tight, compact forms, as just right. In fact, outside of areas with especially harsh conditions, like deserts and high mountains, such a system is seriously undervegetated.
We live on a planet full of life – not just some life, but abundant life. Nature squeezes life into every available space. When we visit a healthy prairie, forest, or wetland, we see plants of all shapes and sizes fitting together to fill the entire area.
By changing our frame of reference to recognize abundant plant life as just right, we can fill our yards with healthy vegetation, and stop fighting with plants to prevent them from growing.