It's how wars can develop when defenses are strong and there is no easy advantage for either side. When invading, the US spent a while bombing Iraq's front lines but advanced rapidly whenever they cleared a path. Russia pushed relentlessly to Georgia's capital with an overwhelming advantage. World War 2 unfolded as a series of crushing Axis victories followed by brutal but effective slogs to push them back again. Various wars against ISIS were punctuated with a lot of substantial gains and losses in both directions. But Ukraine and Russia are mired in almost the same kind of trench warfare that defined World War 1, just with drones and missiles adding to the heavy reliance on artillery and front-line cannon fodder for tiny incremental gains or losses.

As someone else pointed out, the defensive war isn't pointless for Ukraine, since allowing Russia through would put many more millions of people under a brutal dictatorship determined to wipe out their identity. The invasion is pointless but it wasn't up to Ukraine to decide that.