https://en.m.wikipedia.org/wiki/M142_HIMARS
The HIMARS weapon system is probably the most pivotal weapon in the defense of Ukraine behind drones (a distant second, but second nonetheless) and artillery. Why? The reasons aren't necessarily obvious at first, with so many different types of advanced unmanned drone weapon systems what does a rocket fired out of big clunky truck/tank really do to radically change the strategic balance of land warfare in the region?
The answer to that question is among one of the most pressing lessons that the world, especially Europe must learn. Ukraine already learned it awhile ago, that is why they are always asking for more HIMARS missiles...
To explain why this weapon system is so crucial, I think this recent bit of news actually helps explain it best. The US Army is replacing 14 howitizers stationed on Hawaii for defense with HIMARS weapon systems.
Consider the problem as an army (not a navy or air force) detachment charged with defending Hawaii from a possible invasion. Artillery/howitizers are still crucial as they are anywhere else... but their range tops out at maybe 50km with specialized ammunition. Consider the size and scale of the Hawaiian Islands.
The range of a HIMARS system on the otherhand is approaching 500km/300 miles, and you can immediately see how much more useful even a much smaller number of HIMARS systems and ammunition would be for an army detachment defending the Hawaiian island chain than almost any number of traditional howitizer cannons.
It is this scale that the HIMARS system dominates at, and the same logic of choosing a HIMARS system in a situation like the US army faces in constructing a defense of Hawaii applies to a highly contested near peer landwar like Ukraine where the closer you get to the front the more lethal things become.
In otherwords, using HIMARS systems to reach out and strike enemy artillery, radar, anti-air defenses, logistics or other high value targets from the distances HIMARS can fire places the enemy in a situation where all of their forces might as well be stranded on an island with 100km of impossibly fearsome ocean between them and the HIMARS system. You cannot commit your experienced military staff to battle and count on enough of them surviving to continue to effectively fight a war under this kind of consistent, undefendable precision threat.
Traditional tube or cannon artillery is not going anywhere except in unique situations like defending a massive island chain like Hawaii as a ground force, rather the very nature of artillery has been radically changed by the introduction of HIMARS as a new even longer range compliment to shorter range high volume cannon artillery systems. The fact that Russia does not have an effective counter nor even capacity to execute similar strikes at scale makes the likelihood of them making a decisive breakthrough in an offensive this summer remote even with a large advantage in infantry number.