John,
Although Democrats lost the Senate and likely the House, the shifts were minor compared with the presidential race.
Voters, not the Democratic establishment, must choose presidential nominees. Hillary Clinton, Joe Biden (twice), and Kamala Harris were not selected this way, resulting in disastrous consequences (Biden likely won the first time because COVID-19 provided shelter).
Bill Clinton and Barrack Obama broke through this system and continued winning presidential elections (Bernie Sanders and Pete Buttigieg almost did).
Whose fault is it that Harris lost? Democratic Party interference in elections is the primary reason.
Many thanks. Best.