In the Gloria, we sing:
Glory to God in the highest. And on earth peace to men of good will. We praise You. We bless You. We adore you. We glorify You. We give You thanks for Your great glory. O Lord God, heavenly King, God the Father almighty. O Lord Jesus Christ, the Only-begotten Son.
This is evidently a praise chant. But then it follows:
O Lord God, Lamb of God, Son of the Father: you Who take away the sins of the world, have mercy on us. You Who take away the sins of the world, receive our prayer. You Who sit at the right hand of the Father, have mercy on us.
This feels more connected with the Kyrie eleison or related part of the penitential act, where we ask God for forgiveness.
Then, the Gloria closes with:
For you alone are holy. You alone are the Lord. You alone, O Jesus Christ, are most high. Together with the Holy Spirit in the glory of God the Father. Amen.
So, the Gloria still feels part of the penitential act and Kyrie eleison, sandwiched by praise to God. Is thus the Gloria more ritually (and perhaps spiritually) connected with the former, or is it supposed to be a break with the previous part of the liturgy?