The direction of travel would've been the same, but Ukraine might've been able to hold the line for a few extra months. The key part here is that Kursk stunt has no upside to it, and it made an already catastrophic situation worse.

That said, the problem Ukraine had from the start was that it was entirely dependent on the west because it's not able to produce its own weapons. As a result, Ukraine has to fight a war for western media which puts huge constraints on their strategy. For example, Ukraine always holds territory to the last man instead of withdrawing from untenable positions as they did with Bakhmut. I think that Kursk is another example of this phenomenon. Ukraine needed to demonstrate that they still have a capacity to fight, and hence they came up with a narrative that they're able to bring the fight to Russia.

Conversely, Russian army has far more operational freedom because they're not fighting for the media. They're able to make strategic retreats as they did in 2022, and they can absorb incursions like Kursk without diverting troops from strategic areas. Because Russia is self sufficient in military terms, they can ignore whatever narratives are being spun at the time and focus on achieving their long term goals.