You're right, Pepe does have some speed, and that gets him into good positions to cross or beat his marker and set up an easy goal. Sometimes it even gets him into positions where he can apply a finish to a slightly overhit cross.
The problem is that he possesses absolutely none of the skills required to do anything once he gets into those positions. His passing isn't great, his crossing is worse, he can't beat defenders 1v1, and he definitely can't finish.