“Gender” is a bit misleading. For example in Spanish a shirt isn’t literally female. It is just a member of a class of nouns that requires the same articles as female humans. “Noun Class” is the more modern way to refer to these groups, to better reflect that in many languages the noun classes don’t align with human gender in the same way as Romance languages.

In Spanish and Italian the “gender” of nouns is heavily tied up with their sounds, and the modifications and articles used with them help the words to flow more nicely when speaking - similar to how in English we use “an” in front of nouns that start with a vowel sound. French doesn’t do this so much - there’s a lot less consistency with “gender” vs sound, and you kinda have to brute force memorize each word, but French has very different written-to-spoken rules than Italian and Spanish.

The exceptions in Spanish and Italian mostly tend to be loan words, or new words that use the same root as an existing word and get the opposite “gender” to distinguish it.