Flat weeds (eg cape weed and thistles) don’t like competition, anre easily shaded and tend to grow on bare ground, so cover the ground, and they will start to drop out of the mix. Mulch can be applied.
I use the mower and whipper snipper as grass control tools, the grasses that can adapt to my regime grow. This means the annuals often drop out. I don’t worry about the species much, happy to have a multi species mix vs a monoculture, which is hard to maintain.
We have an over reliance on herbicide technology for mine, we do have other choices and landscape management tools.
On the broad acre, grazing management can make huge differences in reducing the need for herbicide and other interventions. In the past herbicides have been cheap and available, hence the reliance on them, often to the exclusion of other land management tools such as grazing, plant recovery, groundcover management etc…
When I started my agronomy career, back in the day, most of the chemical we used are now banned….so go figure… t
This is my field of work 