The mood is positive, but also negative. Where Israel need encouragement, encouragement they get. Where they deserve rebuke, the rebuke is forthcoming.
A leader about to step down from office is entitled to look back on his career and to say critical things about people and events, and that is what Moses does. His audience is Israel, Kohanim, Levites, ordinary people, old and young, men, women and children.
Introducing the leader’s message, however, the Torah could just as well have said, “These are the words which Moses spoke to Israel”. Why does the text actually say, “to all Israel”?
The Midrash gives an answer: “All Israel” includes Moses himself. To whom does he address his criticism? To the people, yes; but to himself too. Indeed, he rebukes himself first, according to the Midrash, before he rebukes the people.
A career in leadership must never blind the leader to his own failings. He has to know himself and acknowledge, at least to himself and to God, that for all that he has achieved, he might have achieved even more had he been able to change himself and work on his own shortcomings.