Whay do you mean by “see the disease”, to see the microrganism?
If that is what you mean, they do see the disease when they are identifying and documenting it. When a virosis is being studied, they go through the motions of getting electron microscopy imaging done. It is expensive and a huge pain in the ass, so it isn’t a viable option for everyday diagnosis.
But then, you are overestimating the meaning of seeing aomething like a virus. You can verify certain structures which exist in some families of virii and not in others, but you can spend the whole day looking at electron/scanning images of virus and all you see is blobs with little blobs in them, and that doesn’t tell you a damn thing. Serum diagnosis is a much more precise way to identify a virus because antibodies and antigens are a key and lock pair. An antibody is present in a certain amount in blood only when a certain amount of that specific antigen is present, there is a direct correlation betweeb antigen and antibodies that has been demonstrated with all of the rigor of the scientific method time and time again for every pathogen that we know. So you can actually argue that the presence of an antigen doesn’t necessarily mean the presence of one specific virus and you might be correct in that assertion. However that doesn’t matter a damn bit because what you have demostrated by testing for antibodies is the presence of specific disease causing proteins which can be treated by a specific drug or prevented by a specific vaccine. So what the fuck else do you want, LED indicators? Some blinky lights?
Just face dude, we won. We’ve had periods in history where millions of people died from diseases we can now threat with a few bucks worth of chemicals, simply due to the uncovered knowledge of microbiology.
I’ll just tell you what I tell all of the other shitheaded vaccine denialists out there. You don’t believe in vaccines? Don’t take them. I am going to take them, and all of the people I hold dear are going to take them. And then when these diseases hit mainstream again after centuries of a worldwide effort to erradicaye them through vaccination, due to your shitheadedness, you are going to die, and I won’t. Best of luck.