The short answer is, the true Church is headed by Rome, and influenced by her
theologically. She’s what the early Church called “the Apostolic See.” But liturgically and juridically, it’s not theologically necessary for all roads to lead to Rome. The pope has virtually no say over what the Marionites’ Liturgy looks like, for example. That’s left up to the Marionite Patriarch. As the last poster said, there are multiple Rites within the Catholic Church – these are related to, but not the same as, the various *sui iuris *Churches.
So to give one example, Pope Paul VI, prior to being Pope, was Archbishop of Milan. Milan uses the Ambrosian Rite instead, originated by St. Ambrose. So it’s a different set of traditions being preserved. Likewise, the Anglican Ordinariate will likely preserve and restore some of the uniquely English traditions within Catholicism, traditions which weren’t practiced or celebrated off the island.
Of the examples you gave, the French used to use the Gallican Rite, but it’s long since extinct. They were always Latins (they speak a Romance language, are part of the former Roman Empire, have a heavily Roman culture and legal system, and so on), so using the Roman Rite makes sense there.
In contrast, the Indian Catholics do have their own liturgical tradition, the Malankara Rite. It’s generally believed that St. Thomas the Apostle ended up there some time after Pentecost. Then, because communications were primitive and travel took forever, the Indian Christians were largely forgotten. It’s said that the Portuguese were shocked to discover indigenous Catholics praying something pretty similar to the Mass when they landed in (if memory serves) Goa.
So given that the post-Apostolic practices of the Indian church were developed in relative isolation from everyone else, it would be a real shame to simply erase that liturgical tradition, so they don’t use the Roman Rite, or pray the Mass . Their equivalent of the Mass is called the Holy Qurbana.
Wikipedia has a good list of Rites within the Church:
en.wikipedia.org/wiki/List_of_Catholic_rites_and_churches#List_of_Catholic_liturgical_rites