From Tall Skinny Kiwi:

The line that bugs me is this one:

“Saviour, he can move the mountains”

It’s not that the statement is untrue because actually, God can do whatever he wants, including the relocation of mountains. It’s just that the particular idea of moving mountains, which occurs most strongly in Isaiah, the minor prophets and later in the Gospels, is almost exclusively in relation to people moving mountains and not God. Jesus told his disciples that they could move mountains. The Isaiah passage [Remember Godspell’s “Prepare Ye the Way of the Lord”], as Jesus enlightens us, was in reference to John the Baptist who would level the mountains and fill the valleys. 

Mountain moving is the job of God’s people!

Yes, our Saviour could move the mountains if he wanted to, but he has commissioned us to move them so let’s get on with it, not in our own might or by human power, but by God’s Spirit (Zech 4:6-7)

The idea behind this lyric, in my opinion, is the same lazy “let go and let God” philosophy that inoculates the people of God from doing anything practical or hands-on because we assume if we just sit back and sing some more songs then God, who is somehow energized by our inaction, will stand up, bare his almighty arm and get things done.