Your first sentence is nonsense. Such assertions undermine your argument.
The Catholic Church is clear that the mark of unity in the Creed can only be applied to the Catholic Church in communion with the successor of Peter (Roman Pontiff). I’m not sure why you would be insulted that Catholics believe that mark applies to the Catholic Church–don’t you profess that it belongs to your Churches and not ours? By definition “one” can only apply to one…
We do acknowledge the existence of eucharistic Churches (a bishop and baptized flock celebrating a common Eucharist) that are separated from the catholic Church. Some of my fellow Catholics in this thread erroneously referred to them as “catholic” Churches–the Catholic Church does not say this (because of the meaning of "catholic), but rather calls them “eucharistic” or “particular” Churches.
Likewise, it’s not about the man you are missing, it is the office. Men who have filled the office have had varied merits and have carried out their duties to greater or lesser extents and have benefited the Church more or less as a result, but that doesn’t mean the office is therefore unnecessary or the duties are not therefore good and important. Nor does it mean the man is sinless or omnisicent or a perfect saint. Just as EOs profess the office of bishop is necessary for a eucharistic Church, especially with regards to its unity, even though a particular bishop may or may not serve his eucharistic Church well at any point in history. So to is the primacy necessary for the catholic (universal) Church in the same way (this is why modern EOs really, really don’t like admitting any universal ecclesiology–it naturally leads to the primacy. Yet, universal ecclesiology is right there in the creed with the word “catholic.”) Even synodality needs a primacy, as the recent attempt at a pan-Orhtodox synod made painfully clear.
If the EO Churches are the one catholic Church professed in the Creed, where was this one catholic Church during the Bulgarian schism? Was it manifested in the Churches of the Bulgarian Exarchate or not? If it was, then did Greek Churches separate themselves from the catholic Church be separating from the Bulgarian Churches? Or, if it was not, did the Russian Churches separate themselves from the catholic Church by professing unity with schismatic Churches? But the Greek and Russian Churches also remained in communion with one another, so one either way, if they are really one Church, they would both have unity and schism with the catholic Church at the same time. This is by definition a contradiction and an impossibility–so they cannot be one.
Even our very irenical Cardinal Kasper, who was in charge of seeking the unity of separated Christians, and who never has a bad thing to say about any non-Catholics,
had to admit “We are increasingly conscious of the fact that an Orthodox Church does not really exist.”