If you included the first part of this history you find the Eastern Arian powers attacking the West and removing all aspects of the Latin Church, before the Western Catholic secular powers gained control again from the Arians.
That is not quite so.
I have never read anyone (until now) claim that the Arians removed all aspects of the Latin church in the lands they occupied. The two churches existed together in the west, the Arian church being usually the smaller, it being originally for the Germanic/Gothic overlords.
However, it wasn’t really one Catholic church in the west, that is a modern notion. The Mozarabic Catholic/Orthodox church was the local church of Spain, where this filique thing got started. They had their own liturgy, elected their own bishops and called their own councils. The church in Gaul was different, with yet another form of liturgy, electing their own bishops and it’s own councils. The North African church was a third, the Celtic church in the islands was a fourth, the Roman church in central Italy was still another.
The way it is often described people must imagine that everyone was using the EF and getting their bishops from the Pope, that didn’t happen until much later. The Latin rite church simply didn’t exist in the way people think of it today, it would be an anachronism to refer to the Christians of most of those locales as latin rite Christians. When the Arian Goths arrived in the west they encountered a population which was not fully converted and a Catholic/Orthodox church that was not centrally governed and not uniform in practice.
And I must repeat for emphasis, the Arians did not remove all aspects of the ‘Latin’ church, although they might have wished they could.
What you consider “too late” or “any usefulness” of the filioque does not view this history with justice, when lives were taken and later in danger of death for it, when the Arians took over.
The filioque was introduced into the Creed at Toledo at the union council of 589AD.
The king (Reccarred) had converted in 587AD. After two brief rebellions the Arian holdouts were subjugated by force, and the remaining Arian bishops renounced their heresy and attended the union Council at Toledo in 589, where among other things the filioque was added to the Nicean-Constantinopolitan Creed.
In other words, the Arian church had dissolved itself and the bishops and priests had become Mozarabic Catholics
before the filioque had been formally introduced. It simply wasn’t needed, Arianism was no longer an organized religion in Spain.
The filioque stands against their teachings of Jesus. Filioque does not work to help them in their errors, filioque calls them out from their errors of who God is.
I seriously doubt that most people even understand the significance of the appendix or why it was put there.
Anyone from one of these aforementioned groups who has the interest and the nerve to read the Nicean-Constantinopolitan Creed in it’s original form will have a concise exposition of the Catholic/Orthodox Faith. In it’s original form the Creed is such a contradiction to what they have been taught they wouldn’t even miss the filioque because it was never really needed in the past and is still not needed.