Most German sentences contain at least a conjugated verb and a component in the nominative - a subject. But many verbs also require another component - an object - in the accusative, dative or genitive. Accusative objects are the most common, but there are also verbs that require the dative.

You've already learned about dative objects that indicate the target or recipient of an action.

Examples:
Wir möchten Ihnen gratulieren.
Ich wünsche dir einen schönen Tag.

To ascribe opinion in a sentence, the dative can be used to indicate whose opinion it is.

Example:
Das ist zu romantisch. – Wem ist das zu romantisch? (= Who thinks that it is too romantic?)
Das ist mir zu romantisch.

When the dative case is used in this way, the adjective is typically accompanied by the word "zu".

Example:
Das war mir plötzlich alles zu viel.
Das ist mir nicht zu schnell.

More:

You'll also come across this way of using the dative case along with the word "genug". Such constructions are often colloquial and used in spoken language.

Die Hochzeit ist nicht romantisch genug. – Wem? – Harry
Die Hochzeit ist ihm nicht romantisch genug. (= The wedding isn’t romantic enough for him.)
Die Hochzeit ist romantisch genug. – Wem? – Julia
Die Hochzeit ist ihr romantisch genug. (= The wedding is sufficiently romantic for her.)