I think that there are some people confusing leaving the parish with leaving the Church.
“Parish shopping” is not necessarily a good term. Maybe “parish seeking” is more appropriate.
We belong to the Catholic Church, which is UNIVERSAL. As such, all of our parishes, whether Latin or Eastern, must adhere to the norms established by the Church. In the Latin Rite, when a parish and/or pastor is not following the norms, rubrics and prescriptions of the Church, and, if this is detrimental to the faith of the person, then, that individual needs to leave the parish and find another parish that is faithful to the Church.
If the CCD program is not up to snuff, and if, for example, the parents find that their children are not exposed to authentic Church teaching, then it is their right to leave the parish in search of one that is in line with the Church.
Perhaps in pre-conciliar days, this issue was not as important because, most, if not all, of the time, the Mass was celebrated according to the norms (EF doesn’t allow for much, if any, deviation) and there was probably a greater sense of unity, as far as CCD was concerned. But, unfortunately, we have many parishes and/or pastors who feel that it is more important to follow the alleged spirit of Vatican II then to take the time to read what the Council documents actually said.
Plus, people protest with their feet and with their pocketbooks. If a parish is not following the norms, then, people will stop contributing and go elsewhere.