I believe these explanations offer us insight into what was the essential leadership shortcoming of the elders. It wasn’t that they were bad leaders per se. Rather, they were only effective local and immediate leaders. Their priority was making the best of Bnei Yisrael’s current abysmal situation. Whereas Moshe and Aharon were great visionaries looking to a bright future when Bnei Yisrael would be guided by the Torah, the elders were focused on the next sunrise. Whereas Moshe and Aharon exhibited the courage necessary to lead a nation into the desert and forge a brand new world, the elders had to show deference to the Pharaoh who could deny their people the next meal. Whereas Moshe and Aharon thought strategically, the elders were trapped in the tactical decisions of the moment, namely, where would they get the straw to make the bricks.
Ultimately, Moshe realized that these elders could not be the ones to lead Bnei Yisrael into the Promised Land. They would be forever stuck in the mud of Egypt. That was their point of reference—end of story. By the time Bnei Yisrael entered Eretz Yisrael forty years later they would be led by a bold new generation of leaders, equipped both spiritually and physically to accomplish their mission.
Relieving from office decent people who are no longer up to the job always was and always will be a difficult task. But what’s true for the army is true for all organizations. The young privates at the front who are risking their lives deserve the very best leadership they can get.