How can love for the Kaaba and the Sacred House be enhanced as the time for performing Umrah approaches, and is not being attached to them considered a sin?

If the heart is not always attached to the Kaaba, then this contradicts the glorification of Allah's شعائر (rituals/symbols) and indicates weakness of faith. This is because glorifying the شعائر is obligatory, and whoever does not love something from them has abandoned an obligation and sinned. The way to glorify them is to strive in supplicating Allah and to be mindful of the virtues and blessings they contain.