World War I was a completely different battlefield than the Napoleonic/US Civil War model. World War II was, again, a completely different beast. As was the asymmetric wars of the next few decades.
Noting the sinking of a Russian warship and the destruction of a squadron or two of warplanes on the ground, not to mention the inability of Russia to obtain air superiority, the differences in combined combat highlighted by the war in Ukraine bear looking at.
The line between infantry and artillery has been blurred. Hand and vehicle carried weapons capable of destroying strategic assets and drones have changed this to a vastly different war. The airplanes the Russian Navy’s Black Sea fleet lost were expensive, but not a particularly useful tool in the way that the conflict has rolled out.
As artillery changed over the ages, the designs of fortresses changed. Thin walls became thicker and then lower - answered by mortars and rockets made to drop in from above (augmented later by bombers - airplanes being a version of mobile artillery which also has recon functions).
The mass introduction of hand-held antiaircraft weapons first protected the “sitting duck” convoy of the Russians and then, in Ukraine’s hands, prevented Russian aircraft from promoting air superiority. Similarly, hand-held anti-tank weapons allowed infantry to blunt the shock value of tanks - a form of armored mobile artillery as well as light weight anti-ship weapons to be able to neutralize the floating artillery of the opposing navy.
The introduction of highly accurate Western rocket artillery and howitzers introduced to Ukraine have been answered by less accurate, but more numerous artillery and missiles on the Russian side.
And finally, the extensive use of drones, both as artillery and for surveillance/recon has been another game changer.
We have entered a war of attrition where neither side has sufficient resources available at the front to take decisive action, and while Ukraine can strategically damage Russia, Russia could, should it feel it is desirable, literally flatten Ukraine.
So, other than the war going on “forever” (which likely would mean that Ukraine’s resources would be depleted before Russia’s), at some point this war will reach a point of equilibrium - unless NATO decides to intervene to assist Ukraine in pushing Russia out of its pre-war territory - with the assumption that Russia will not give up its annexation of Crimea any more than Israel would give up the Golan Heights. By then, Russia’s ground-based military should be softened enough not to be a threat and, as long as the Russian boarder was not violated, the threat to Russia would not be existential.
But, getting back to the original concept, the foot soldier now has the same punch as air/naval/armored artillery did in the past and the benefit/cost ratio of using expensive planes, ships and tanks in the conflict has dramatically shifted.