Is the aforementioned statement major shirk because it attributes control over worldly affairs to the world itself and expresses discontent with God's decrees, and is it permissible to continue with the engagement?

Statements that express discontent and impatience with God's decrees and show ill-manners towards Him, even if blameworthy, are not major shirk (polytheism) unless the speaker intends that time is the independent agent, which is something hardly ever uttered by a Muslim.

The categories of reviling time are: 1. Pure narration without blame: Permissible, such as complaining about the intense heat of the day, like the saying of Lot (peace be upon him): "{This is a distressful day}." 2. Reviling time with the belief that it is the agent: Major shirk; due to believing in the existence of a creator alongside God. 3. Reviling time without believing it is the agent, but because it is the locus of the disliked event: Forbidden, but does not amount to shirk; because in reality, it amounts to reviling God who controls time, and this is foolishness and error.

Merely quoting a statement does not necessitate affirming it. Therefore, one who quotes disbelief does not become a disbeliever unless he affirms and believes in it. It is advisable to educate, alert, and advise the man if he is a person of religion and good character, instead of breaking off the engagement.