Well, they’re probably not obsolete when used properly, with sufficient support, and in the right circumstances.
But as a “one size fits all” tool to just throw in mass quantities at the enemy, no matter the situation, well, that’s been a poor strategy for many decades before this.
The war is showing that tanks are rapidly becoming untenable for defensive and occupation purposes (which they were never all that well suited for anyway) but remain dominant in the offensive role _when properly supported by infantry, air and artillery_. The Russkis seem to have forgotten that important element.