You are right to a point. Certain pests can get out of control because of garden conditions. For example if you over fertilize, you can get lots of lush green growth which can be attacked by aphids. Certain pests are designed to attack certain plants and it is not to eliminate them in nature, but to keep them in check. Like the borers that old rugosa rose stems will get. If you've ever seen rose rugosa growing wild, you may know that it will spread creating large patches. So the borer killing off the old stems helps keep the rose from overtaking everything. Sometimes it is the weather conditions that cause perfect conditions for a pest. So one year you can be perfectly fine and the next have a problem.
To keep pests in check, attracting birds to your garden can help. Birds eat lots of pests. I found that the sawfly larva problem I had on my roses diminished after working on attracting birds to the garden.
Also working on having plants in successive bloom attracts beneficial insects.
Even if you are not into flower gardening, having plantings really will help the health of the vegetable garden in my opinion.
I've found the longer I've gardened here the less pest problems I have had, but I know that I can always get an out break of something at any time. Oh and having tolerance for a not picture perfect garden helps too. Some people get all nuts over seeing few spotted leaves, etc. when there is nothing really wrong. Knowing you insects help, some insects are fairly harmless while others need be eradicated quickly like Red Lily beetles.
I have no clue about grubs eating cabbage roots. I hope someone post who does.
Remy

We recently had a similar discussion on my hummingbird forum. As Remy stated your deduction is partly right. I also think that using natural fertilizer and compost keep your plants healthier than using chemicals. Another plus is that you don't have to worry that the chemicals will cauze harm to beneficial bugs and birds.

Ken Druse says that bugs are programmed not to destroy their hosts, nor to do so much damage that it is really obvious, because this would attract the attention of their predators. Thus, in a well balanced environment damage should be kept within reasonable bounds. Another thought, critters are programmed to live in harmony with native plants, so if your environment contains natives it will also attract more birds and predatory insects than if it is all exotics.

Read a book or two by Eliot Coleman or on biodynamic gardening.
https://www.biodynamics.com/biodynamics

-Rosalinda

I consider myself part of nature. If a pest is eating my food, in my food garden, I have a natural right to do something about it. First I learn about the pest and then if it's a bad infestation, I get rid of the pest with my fingers, water spray, traps, etc. I keep the soil really fertile with lots of compost added all the time.

But the weather conditions and/or timing of planting/egg laying can affect everything. Some years are bad for one disease or insect, other years are good. Some things you just have no control over.

Sometimes bug holes induce the plant to produce growth hormones (auxins), which is good. Sometimes I have to pull out an infested plant and throw it in the garbage. They are living things. Some are just bad seeds with bad genetics.

I have given up on root crops because of voles. I hate crying in my garden over lost plants, and hate daily trapping of rodents, so I don't plant what they love to eat. I also gave up on crocus and tulip bulbs, except for when I'm in the mood to plant them with wire cages or crushed seashells(grit) around them.

It's not just the soil, it's the whole surrounding environment that affects the garden. That's life. Do the best you can, squish the bad bugs or flick them into a can of soapy water, and avoid stress (for yourself and your plants) when possible.

Good luck with your new gardening skills. You never stop making mistakes, observing, experimenting, and learning.