What do you mean by saying that? We shouldn't balance around the player winning in the same way the AI does?
There are two types of snowballing: Fair and unfair.
The unfair type is when there are critical breakpoints that allow the leader to turbo-charge their lead and leave everyone else in the dust. For a while Ideologies gave 2 free tenants to the first person to pick them, which meant the AI that was already leading got 25,000+ culture for free. That was deemed unfair, and was fixed. Unfair snowballing mechanics are characterized by 2 things: 1- Massive surges in power from a single breakpoint 2- Exclusivity to the leader(s)
If the first person to say, reach archeology, can build infinite archeologists and take all the dig sites before anyone not neck-and-neck gets to grab any, they get a buttload of advantage, and everyone else loses out on that by default.
Meanwhile something like the massive military power spike from Knights are not deemed unfair, because while the advantage is very big, everyone else can simply research the tech and make their own. (Though Artillery had a much bigger power spike that was deemed unfair, because you couldn't fight it off like you could knights, so it was broken into field gun and then artillery. The problem there was that while you can defend vs knights until you research them, defending against Artillery was basically impossible and if you got it first you could just demolish your neighbors with absolute ease.)
The fair type of snowball is something we should not aim to change. It's just the fact that new techs unlock better stuff, so you get more than you had before. More production builds more things, so you get more than you had before. More culture unlocks more policies which give more yields, so once again you get more faster.
Unless you don't want to be able to upgrade your tiles, unlock buildings, or have policies with text, the game will by it's nature have snowball mechanics. We can tone down unfair power grabs/spikes, but to remove snowballing entirely would be to play a different game entirely.