In the Autocephalous Catholic movement, there are a number of different groups. As I know you are aware, dear long-time readers, I have an obsession with purity of identity. I believe strongly that you should be what you say, and you should know what you are. One of the greatest problems of the Old Catholic tradition (or really any of the Autocephalous Catholic traditions) is that there are a number of individuals who enter not because they believe in it, but because it is a place for them to exercise orders. The problem with this is that these individuals are not truly wedded to their identity as Old Catholics. Therefore, there is no real interest in learning the theological necessities.
I freely chose this tradition. This may sound like a mad thing to say, given the present situation, but I theologically adhere to the principles of the original Church of Utrecht. Whatever they think about us, their wayward children, is irrelevant because they have not made universal jurisdiction and the supremacy of the Archbishop of Utrecht to be a central tenet of the faith. It was not such before Mathew left the Union of Utrecht and it still is not.
In very rudimentary summary, the Ultrajectine tradition includes the preeminence of the local church united around the local bishop as well as the primacy of theological conscience. The Ultrajectines were accused of using this to adhere to Jansenism (which meant a lot of different things to a lot of people) and later it meant rejecting the dogmatic (that which must be believed for salvation) pronouncements of things like the Immaculate Conception, Papal Infallibility, and the Assumption of Mary.
There are still others who will use the moniker of Old Catholic when they are, in fact, dissenting from the Roman Catholic Church. These individuals' canonical status is specific to them. Canon 754 is very clear that "All the Christian faithful are obliged to observe the constitutions and decrees which the legitimate authority of the Church issues in order to propose doctrine and to proscribe erroneous opinions, particularly those which the Roman Pontiff or the college of bishops puts forth."
There are many people on this spectrum, both right and left. Some have chosen to separate from the Roman Pontiff due to a desire to seek ordination outside of a local Roman Catholic bishop due to gender, marital status, orientation, liturgical preference, etc. Regardless, they are formally separate from communion with the Roman Pontiff and are, therefore, in an impaired communion. There is no such thing as Roman Catholic except for jurisdiction because of Vatican I. In this, they are guided by their own conscience.
For Ultrajectines, this is not a problem because we do not subscribe to a Ultramontanist view of papal authority and church structure and left before this innovation. But, there is a vital imperative that those who claim this name and this tradition understand what it is about and why we exist. This is not a consolation prize. This is not a "we're like them but..." For me, I want to invest in something with my very valuable time and resources that I absolutely believe in and hold. Unfortunately, it is a bit of building from the ground up. And we have to work harder to catechize people who come to us and explain the difference. But, I think it is worth it to let them know that we really hold our faith dear.
It also does not necessarily mean large numbers. The remaining Old Catholic Churches in Western Europe are infinitesimally small compared to other traditions. But, we have as our inspiration one who left the many to chase the few.
“Do not wish to be anything but what you are, and try to be that perfectly.” - St Francis de Sales