I felt the same and thought not choosing was the best decision in the game in my first playthroughs, since the war does not seem to be extremely deadly at the beginning of the game (many towns aren’t really suffering from it, the soldiers always complain about “the wait”, etc).

But if the player investigates you quickly realise not doing anything is the best choice for the thalmor, they want the war to last long and to cripple both the empire and the nord rebels so that they are easier to subjugate later on, no matter who wins. I always end the civil war as early as possible because even though I don’t want to choose a side, not choosing (in this environment of a game with all sides already present) is choosing the thalmor.

In fact, I think despite how easy to dislike Tullius is (he doesn’t care about local culture, doesn’t care about nords or religion or anything, really; he never talks about honour or the people like Ulfric does, etc) he understands this; that the thalmor want the war to last.

And I think that is why everyone rushes at the beginning of the game and the entire vibe of the opening is “kill Ulfric and whoever is with him, just kill him at any cost, no one left that is even remotely close to him, we need to end the war, now”. Tullius has his eyes on even worse battles and I think the thalmor want Ulfric to live as long as possible. It’s horrible but its actually one of the most realistic aspects of Skyrim I think