It is an interesting risk assessment worrying about engineered viruses, when we are literally surrounded by them and any of them could mutate and become dangero

It is an interesting risk assessment worrying about engineered viruses, when we are literally surrounded by them and any of them could mutate and become dangerous. I have always assumed that an engineered virus specifically engineered to not transcend its limits would be less likely to become a problem than all the other viruses whose ability to mutate around our immune systems is required for them to survive more than a few years. Or is there a factor I'm unaware of, such as the the most useful sources to work from are also the most virulent with nasty behavior just one mutation away from being switched on?