If they are losing more then surely it would eventually get to a point when we start to see a Ukrainian breakthrough and likely even higher losses/captured.

I am not sure politically Ukraine would go for a massive breakthrough, maybe, but what I think is more likely is Ukraine will slice russia's purposefully diffused offensive lines up into little pieces (since russia optimized for small unit infilitration, this is the unavoidable tradeoff, russia has no concentation of power and no authority over moving large concentrations of power), enclose them and simultaneously pull off large sections of russia's frontline forces from the board leaving the rest in panic.