What I had in mind of a Catholic who holds the full faith but attends NO would be one who grew up, was catechised before the V2 reforms and then just continued going to Mass without questioning it after V2 - because well, why would they assume the Church had suddenly flown off the rails?
Firstly, that generation is mostly dead. Secondly, i've talked to many in that generation and everyone knew that V2 was a change. The new mass was such a stark, quick and violent rupture with the past that it shocked everyone. No one could hide from the changes. You either accepted them through "obedience" (knowing the changes weren't right), you accepted them because you were a liberal at heart who wanted an "easy" Church, or you walked away from the changes and became a Trad.
Such a person could be completely unaffected by V2 novelties.
The only people who didn't realize that V2 was different, were those who didn't know their faith beforehand.
Furthermore, there are tons of conservative NOs who were born after V2 who reject ecuмenism and BOD,
There are many more heresies of V2 than ecuмenism and BOD. How about "religious liberty"? How about no salvation outside of the Church (this is separate from BOD)? Then there's the moral issues which have/will damn many others, even if they reject ecuмenism and BOD - NFP, false-annullments, gαy civil unions, voting for pro-choice candidates, condoning family members who apostasize and become pagan or protestant, accepting sex-ed in schools, accepting euthanasia, etc, etc. All of these "social issues" are promoted by the local archdiocese. Even if one attends an indult mass, you are exposed to these dangers to your faith, these temptations to sin, these temptations to compromise. These dangers are not inconsequential.