Learn Italian: Avremmo voluto l'apporto di tutti loro per il progetto congiunto. - We would have liked the input of all of them for the joint project.

When combining the quantifier tutto with a stressed (tonic) personal pronoun like loro, noi, or voi, tutto comes directly before the pronoun and matches it in gender and number. Unlike when tutto is used with a noun (where you need a definite article, like tutti i progetti), no article is used between tutto and a pronoun. So, "all of them" is simply tutti loro.

What if the group of people we are talking about was entirely female?

Then you would change the quantifier to match the gender: di tutte loro. The pronoun loro stays the same because it is gender-neutral, but the quantifier tutto must always reflect the gender and number of the people it refers to.

Avremmo voluto means "We would have liked". Why use volere (to want) instead of piacere (to like)?

English frequently uses "would have liked" for unfulfilled past desires, but Italian naturally uses the past conditional of volere (avremmo voluto, literally "we would have wanted"). You could technically say ci sarebbe l'apporto... (the input would have pleased us), but avremmo voluto is much more direct and idiomatic for expressing a clear intent or wish that didn't happen.