You get the message you want to hear. The message depends on the person burning it. Usually it’s dissatisfaction with something being done in the name of America that the person/people want to make known. Because people get so uppity about free speech applying at all, and especially applying to flag burning, it’s an effective statement to get the press. But those who believe the one-note-charlie rhetoric about “what it really is saying” aren’t swayed. But rational people are.
The right has been claiming exclusivity to the flag for some time and it’s a shame. The flag is for all Americans but when it’s usurped by the use of only a few, that’s what’s being burned. The deeper American values are what’s being represented when the flag is burned.