If I go into my garden now, and pull up all the weeds, the garden will look good for a bit, and the nutrients they were stealing from other plants will be spread out amongst the remaining plants.

However, there are likely some smaller weeds just under the surface, so within a few weeks, there'll be some weeds again, and they'll begin taking nutrition away from all the other plants. A year from now, there'll be just as many weeds as before, and they'll have strangled and starved many of the other plants in the garden.

It's generally accepted that there's two ways to deal with such weeds.

1. Regular maintenance. You need to cull all the weeds, every week, to keep on top of them. Eventually this will weaken the roots, rhizomes and seeds and then there'll be fewer weeds. Over time there'll be fewer weeds to remove each week, but you must never stop maintaining, or else they'll take over as before.

2. Preventative measures. Look at the circumstances that cause weeds to form, and make structural changes to stop this. This may include things such as ground-cover plants, which protect the soil from weed growth, but store and then distribute their nutrients back into the soil. It can also include things like organising, supporting and strengthening your other plants, using things such as companion planting (where two plants take and release opposing nutrients, both working together and feeding each other to become stronger). When the garden is unified and stronger and working harmoniously, there are fewer opportunities for weeds to thrive.

It's best to take both approaches simultaneously.

Oh, sorry, I accidentally posted this gardening tip in a comment about billionaires!