Dulzura translates to "sweetness" and is a beautiful, evocative word that goes beyond just taste.
In this song, the artist uses it to describe the tenderness and affection in a relationship, singing "sin tanta dulzura" (without so much sweetness) and later referring to "tu ternura" (your tenderness). It captures the emotional warmth and gentleness that the singer misses or regrets not having experienced more deeply.
Have you ever been in a situation where someone led you on, and then, out of nowhere, they tell you it was "por diversión, no para enamorarse" [for fun, not to fall in love]? That's exactly what La Energia Nortena is singing about in "Tan Fácil." The singer is heartbroken, wishing the other person had been honest from the start.
He keeps repeating, "Tan fácil de haberme explicar" [So easy to have explained to me], lamenting that it would have been so simple for them to say they didn't want him in their life, or that it was just for physical affection. He wishes they had told him "que no era el momento de verte conmigo" [it wasn't the time to see you with me] before he developed feelings. It's a really relatable song about the pain of unrequited love and the regret of not seeing the signs sooner.