Hi there.
Yes you are quite right that rotation has it's place. However that is mostly intended for large farms. You do not know what was planted where by the previous holder. One chap on our site had planted his onions in the same place every year and after the 18th year complained that they had a disease.
Companion growing is important. I found this year my carrots were free from carrot fly. I had tried growing a row of onions and a row of carrots in the past, carrots in raised pots based on a theory that the fly only get to 4" off the ground (wrong). wiped with a strong smelling fluids. Nothing had worked. This year I had a load of marigolds, just to make the area look pretty I planted them round two rows of carrots (which I already knew were doomed) and was delighted to find that there were only one or two carrots with fly damage.
Things of the same 'family' like potatoes and tomatoes or the onion,leek,garlic groups are best kept separate but on a plot the distance between where you can grow one or another means that fungal spores are capable of getting blown from one end to the other, or even from next door.
When I first started, I thought that you just dug up everywhere in Autumn put on a layer of rich organic matter. In spring dig in the manure. Plant the crops in neat rows, keep weed free scatter a few slug pellets after it rains then enjoy my veg when ever I wanted them.
Then I found that the cabbages were too small, the cauliflowers were not formed properly, parsnips looked like weird monsters from outer space, the potatoes had holes in them, sprouts were all open. Beetroot bolted, spinach went to seed, the broccoli turned in to yellow flowers, tomatoes got blighted and the courgettes became marrows overnight. Beans got so huge they were stringy.
The herb bed was so full of nettles I could not get a sprig of mint without being stung.
Over the years, with different plagues, unreliable weather and weeds which attach themselves to roots, I have learned to grow herbs in big pots, cut them well back in mid June for a second sprouting. Grow the vegetables we like in smaller numbers, spacing out better, I still find it hard to realise that the little 3" cabbage plant will soon span to 3 feet.
This year we heavily manured a bed with about 2ft of fresh manure in February and we planted it with courgettes which needed to be picked daily. Next year we will use the same bed for potatoes. Later that year it wont get any more manure but will have winter onions planted on it.
I just lift the weeds now when I want to plant sprouts cauliflowers or winter broccoli, they like the ground hard. So it will not be dug.
Picking at the right time with beans gives me more crop and the beans can either be eaten, frozen, given away or composted, not left to go stringy.
Spring is my favourite time, freshly dug weed free ground and little seedlings offering promise.
The science of growing crops is not too much different to the science of parenting a bit hit and miss and you are never too sure how the end product will turn out. But the plants do not talk back to you or run off and go missing. And if crops fail one year, you can try again the year after.