Antibiotic or no antibiotic in case of viral outbreaks like IB, ND, AI & IBD?

In my opinion and logically, I must say yes, because one shouldn't leave the bird on the mercy of viruses and bacteria, one must try what burden of the birds can be reduced by helping in killing those organisms by remote help. And in my experience I would say a clear NO, because whenever I tried it the mortality rose up multiple times and in the same flock, removing antibiotics reduced mortality. I'm just a DVM and confused over this issue, as in human medicines, antibiotic therapy is imperative in case of viral outbreaks like influenza, chicken pox, and more recently, during Covid-19 azithromycinrme is the drug of choice in the TREATMENT of the disease.....! I seek the help of our experts in medicines, microbiologist and pathologists in understanding the process and why antibiotic use increase mortality in the case of vital diseases in poultry only....? ??