Life would not exist without germs! They are a vital part of us. They live on every bit of us and particularly important in our guts where they help break down our food and can also make certain nutrients for us.
We probably evolved from germs! Any even if we didn’t there’s a theory that we have bacteria in every single one of our cells. In our cells we have thing called mitochondria that make energy out of food in our cells. We don’t know exactly how these came to be there but there’s a possibility that these started off as bacteria that our ancestor cells consumed and developed a symbiosis with (both living together and benefiting). Mitochondria have their own DNA which very similar to bacterial DNA. We get our mitochondria from our mother.
To add to Jean’s answer, plants not only contain mitochondria, which were probably started off as Proteobacteria, but also chloroplasts, which probably started off as Cyanobacteria. Chloroplasts, contain the pigment chlorophyll which gives plants their green colour. This is where photosynthesis occurs, converting energy from the sun into chemical energy for use by the plants, and eventually for use by the animals that eat the plants, and finally the animals that eat the animals that eat the plants!
So between multicellular organisms evolving from bacteria, mitochondria, chloroplasts and the 500 to 1000 bacterial species which live in our stomach to help us break down food (there are ten times more bacterial cells in our bodies than human cells!) most types of life wouldn’t exist without bugs.
Also, life without bugs would be very boring as we wouldn’t have certain types of bread or beer (brewer’s yeast), some wines, cheeses and yogurts (lactic acid bacteria) and very short as we wouldn’t have antibiotics which are produced by bacteria and fungi!
Finally, scientists use bacteria such as E. coli and fungi such as yeast, as “model organisms” to carry out important experiments, ranging from genetics and cell biology to cloning and evolution.
So, in my opinion, although bugs cause lots of disease like tuberculosis, food poisoning and pneumonia, their contribution to life outweighs their downside.