It depends on the language. Operas sung in German are easier to understand because it is a much more articulate language. English is not a great language for singing.Soprano Anna Moffo is very easy to understand. Some singers just slur more.
This old oxymoron NASCAR redneck loves Opera, and there is only one real American/British language opera which is Porgy and Bess.
Italians wrote the book with Opera, with the frogs and finally the Germans following.
I read the text, and watch the captions...and when it is La Boheme, get tears in my eyes every time.