When someone quotes a statistic about “Catholics”, they need to follow up with a clear definition of whom they are speaking.
In the mid 1950’s, Mass attendance was somewhere between 60% and 70%. It has gradually been going downhill since then to somewhere between 23 and 25% (source, CARA).
So if someone says today 50% of Catholics don’t follow the moral teaching of the Church, we need to see if the 50% they are speaking about are those attending Mass regularly (which 50% would actually be about 10 to 12% of all Catholics), or anyone who self-identifies as Catholic (which includes the @75% who don’t attend Mass regularly.
Another statistic is the one trotted out about how many Catholics follow Humanae Vitae (often cited as 20%), so it is again debatable as to who exactly we are talking about.
Then we can slice up the demographics further, to those who were well catechized (those born well prior to Vatican 2) and those, perhaps, being catechized post 1990 when catechesis, at least in some areas, took a turn for the better.
The short of it is that we have a lot of people who were baptized but no longer practicing, and many of them if not the great majority of them were never catechized much beyond a pablum goo of loving one another (without any clear definition of what “love"means”).
To answer the OP: To be Catholic means following the Magisterium. To be fully Catholic is to be fully Christian; the two are not separable