Jesus was about to speak to them.
And there was much rejoicing.
So it is somewhat with Catholics. When the Gospel is proclaimed, it is Jesus Himself who speaks to His people in His own words. That is just crazy cool. And so there is a little rite all of its own called the Gospel Acclamation to psych us up for it. The definition of acclamation is that of a loud and enthusiastic approval. Singing he Alleluia should be like, “OMG! - literally! - G is about to talk to us! This is so awesome. Everyone pay attention! Shh! Shh! Shh! Here it comes! Huzzah!” It should not be “All . . . le (YAWN) luuuuuuu - yah. Whatever.”
Perhaps it is that it is too easy to become accustomed to even really great things.
The “Alleluia” itself is to be sung by everybody while standing, led by the choir or cantor while the verse is sung by the choir or cantor. It is always sung except during lent when another acclamation is sung.
It may be difficult to sustain the excitement week after week, day after day for this. It is like playing a game that you know you will always win. “Yay! I won again.” But at least it should remind us to smile in our hearts.