What made wwi trench fighting especially terrible? why, when asked, do the majority of historians say that wwi would be the war they least want to fight in?

In the trenches there was this thing called trench fever, it was caused by the spread of lice in the filthy trenches. Historians would probably say that it would be the least likely they would fight in because of how bad it would get in the trenches, going weeks or even months without a shower. Also the fact that it was one of the bloodiest wars in history