It certainly was in AD 70 when Christ allegedly "removed the kingdom from old Israel and its leadership and passed it on to the holy nation under the authority of the apostles".
The RCC was not challenged in regard to its apostolic authority for nearly 1000 years. Clearly the RCC would have a legitimate claim to being the sole legitimate authority for Christ's kingdom if Christ actually set up his ruling kingdom on earth in 70AD.
I realize you are desperate in wanting to tag all non-dispensationalist as Romanist
No. Using your logic and theology, Reformation Preterists would not be Romanists. They would be apostates.
What history books are you reading?
There was no Roman Catholic church in AD70. There was no hierarchy and all the trapping we associate with Romanism. Your logic is failing you.