"This texte isn't dificult. It's easy." = Ce texte n'est pas difficile. Il est facile"
"C'est facile" is more general and not used when the subject can be "touched" (real).
I'm learning English, it's easy = J'apprends l'anglais, c'est facile (you can't really "touch" the fact to learn a language)
I did an English exercise. It was easy = J'ai fait un exercice d'anglais, il était facile. (you can touch the paper ^^)
NB: In french, repeat an idea is not "élégant". In french "This text isn't dificult." means the same that "This text is easy" because "difficult" and "easy" are opposite words. So we says "Ce texte n'est pas difficile." or "Ce texte est facile" but not the both in the same sentence.
About your second sentence "I like this city because it's beautiful" = "J'aime cette ville parce qu'elle est belle" (the city can be "touched").
I hope I helped you.