"The Most Honest Three Minutes In Television History"

So what this character is saying is:
1. The USA is not the best country on Earth.
2. It used to be.
3. MAGA

Ironically this came out during the Obama years so his message was close to that of a soon to run for President named Donald J Trump.

Why do people on the “left” revere this films message and reject MAGA?

Love your work Jeff Daniels. Please remember that no country on Earth has enough freedom.