Robert E. Lee
There definitely seem to be combatants that enjoy at least some aspects of war. If you look at the historical military literature, including poetry, it is not all just negative.
It is true that with increasing industrialization of war during the last 150 years, the overall tenor has changed.
To such men, please note: life never really ends, and you and your offspring gets eternally impacted by all miserable and soulless destruction of life's beauty you may have caused, inflicting more hardship and perpetuating novel state of misery upon flocks of others.
Every reality has at least two versions of it, or more.
War seems to rewrite the brain. People are miserable and bored most of the time, are terrified while in combat, and come back with psychological issues we're still just beginning to understand. It's hell. And yet, people do get addicted to the mayhem and the rush. The mercenary life is attractive to a lot of people. There's still a lot being debated here, but one of the theories about PTSD is that much of the damage is done (or, at least, is made permanent) when people return to civilian life. Having been exposed to life-or-death situations, they find daily life to be low-stakes and artificial; the time in which they were most alive as in combat (even if they hated the experience and what it did to them).
Still, I agree that actual war is not at all "fun".
Well an idealized version of war that’s designed to glorify it could be fun.
Is actual war fun? Is the Ukraine war fun? I doubt it’s fun for any of the participants. It’s not fun for Ukrainian soldiers, it’s not fun for Russian soldiers, and it’s not fun for Russian or Ukrainian civilians.
Maybe it’s fun for some onlookers that like to cheer and spectate, but I would argue that speaks more to the nature of the spectators than to the nature of war.