Obviously she was not everyone's first choice. She was almost no one's first choice. Democrat voters let her know that when they only gave her ~7% support in the 2020 primaries. Maybe a messy primary that everyone feels a part of would have been better than a few leaders of the Democratic party attempting to anoint the next president. Maybe you think it was the responsible choice, but that certainly isn't what Obama thought in 2024, since he was pushing for open primaries before his hand was forced into endorsing Harris.

Bernie Sanders and Elizabeth Warren both performed significantly better than Harris did in the 2020 primaries. Maybe one of them would have been the responsible choice.