As I observed in an earlier post, any teaching that fails to comport with the formal doctrines of the Catholic Church would qualify as a theological error.
In the New Testament, elders (bishops") were ordained and appointed by the apostles, and/or by bishops who had already been appointed by an apostle. So, then, can your so-called "elders" trace their episcopal succession back through Christian history to the apostles themselves?
Given that the two are identical, I'm going to have to disagree with the opinion that you've been taught by your chosen recently-invented, man-made non-Catholic sect.
The first use of the phrase "Catholic Church" as a technical term to refer to that one historic Church founded by Jesus Christ himself in 33 A.D. was by St. Ignatius---the 2nd-century Catholic bishop of Antioch. "Catholic Church" is simply another, more technical, term for the universal church.
It is the very same proof that the first Christians offered in the 1st century. The apostles said, "We are the authoritative leaders of Christ's one historic Church and, as such, our teachings are true and binding, identical in authority and truth with Jesus' own teachings (Lk. 10:16; 1 Jn. 4:6). Since our Church was in fact founded by Jesus Christ himself (Mt. 16:18-19)---and since Christ himself has endowed us with his own power and authority (Mt. 28:18-20; Lk. 10:16; 1 Tim. 3:15)---the teachings of our Church are therefore infallibly true and binding upon believers." Now imagine a 1st-century skeptic replying, "I do not recognize your Church as Christ’s Church. I prefer the Arian sect and choose that as my 'church,' or perhaps the gnostic sect down the street!" How do you think the apostles would respond?
Of course not---because, like your own chosen sect, the JWs was not founded by Jesus Christ himself, but rather by a mere man (Charles Taze Russell) during the past five centuries (1872 to be exact).
"Scripture" as infallibly and authoritatively interpreted by whom? Again: Who possesses that inherent authority? Who or what has been endowed by Jesus Christ himself with his (Christ's) own power and binding authority? Charles Russell? Joseph Smith? The human founders of your preferred recently-invented, man-made non-Catholic sect? Or is it that one historic Catholic Church founded in 33 A.D. by Jesus Christ himself and led by the apostles/bishops that he himself endowed with his own interpretive and doctrinal authority?
"...with Scripture" as infallibly and authoritatively interpreted by whom? Who or what possesses such inherent doctrinal and interpretive authority? You? Your chosen man-made sect? One of the other myriad recently-invented, man-made non-Catholic sects in existence today, with more being fabricated every week?
"Scripture" as interpreted by whom? You? Your man-made sect? The Catholic Church? Again, the question of ecclesiology ("What is 'the Church'?") must be definitively answered before one can appeal to Scriptural debate as a basis for solving theological questions. Whose interpretations will we accept as authoritative? Which of our "churches" has the infallible, authoritative, and Christ-endowed ability (and responsibility) to interpret the Bible is a way which is binding upon believers? This must be definitively answered before we can proceed to biblical debate.
For me, the first error that comes to mind is the anti-sacramentalism that exists in your belief-system, which is most specifically evident in your doctrine of the Eucharist (Lord's Supper). By contrast, you can view the Catholic teaching on the Eucharist HERE.
Because one is either ordained and appointed through the laying on of hands by an authentic bishop of Christ's one historic Catholic Church---and therefore receives the Sacrament of Holy Orders, and is thus endowed with Christ's own power and authority---or he cannot rightly consider himself a legitimately qualified leader in the one historic Church of Jesus Christ. In the New Testament and throughout Catholic history, bishops can only be ordained by other true bishops.
Already did.