Sabotaging is much too strong a word. The fever is not essential to the immune system. If taking down the fever makes it easier to cook food or do something else that is important to you, go ahead.

We have had fever suppressors for so long now that we know they are not harmful to the immune system in any meaningful way.

A fever should be temporary. If you go several days with 39 C then something is wrong and you should absolutely seek medical help. People used to die from simple bacterial infections before we had antibiotics.

And be mindful of the children! Small children are wired somewhat differently and you should be much more careful with them. 39 C in a newborn can be life threatening.