I know Liturgy is not what the Holy Father is discussing in this (as usual, brilliant,) homily, but I think his warning that Faith is not subjective sentiment functions as a condemnation of the attempts to fabricate Liturgy according to ones own taste, according to what makes you feel a certain way, what you like.
All too often...we find ourselves immersed in a world that would set God 'aside'. In the name of human freedom and autonomy, God's name is passed over in silence, religion is reduced to private devotion, and faith is shunned in the public square. At times this mentality, so completely at odds with the core of the Gospel, can even cloud our own understanding of the Church and her mission.
We too can be tempted to make the life of faith a matter of mere sentiment, thus blunting its power to inspire a consistent vision of the world and a rigorous dialogue with the many other visions competing for the minds and hearts of our contemporaries.
I may disagree with the direction some in authority over me might take, (in contravention ISTM of the direction those in authority over them, and Those in authority over them, ask us to take,) but I refuse to indulge in, to quote a commentator on TNLM called Tobias, "pessimism that excludes consolation."