Perhaps I sould have qualified my "every" with "most". But the point remains valid. Of all commanders during the war, Lee had the highest overall percent of losses.
But how about CSA Gen John C. Pemberton (Vicksburg, Champion's Hill, Chickasaw Bayou) who had 50% losses? (Source: Attack and Die)
Lee lost about 20% of his men during the war. Grant lost about 18% of his. Not all that much different.
Now let's look at Lee versus Grant. Lee lost about 40,000 men against Grant, while Grant lost 60,000 against Lee. Grant had bigger armies (almost twice as large as Lee's) and the ability to call in more troops while Lee didn't.
Do you think that Lee, second in his class at West Point, could not figure out what Grant was doing, while Ditto the armchair general could?
Both of them suffered heavy losses attacking well entrenched foes. The lesson to be learned from both generals and the war in general is don't send your troops in charges against a well entrenched foe unless the objective is worth the cost.