Leaving aside the 'should religious state schools exist' debate, Catholic schools vary hugely.
20 years ago the Catholic schools near me (London) were the ones that were undersubscribed, with attendees being working-class Irish families, traveller kids and those who were new to the area and didn't know how to apply to other schools. Some were good schools but not seen as desirable.
Then loads of Poles with some other Eastern Europeans and Portuguese and Brazilian families arrived, making all schools oversubscribed but particularly the Catholic ones. Then there was a dip as many of the Polish families didn't want their child in an all-Polish class so didn't apply for Catholic schools - now there's more of a mix and the families generally speak English so that's less of a driver. But it does mean the Catholic schools are 100% Catholic, with the only exceptions being those with an EHCP.
I considered one Catholic school for ds - it's our nearest secondary, the only one in walking distance, has an excellent reputation for SEN and generally - but he would be the only non-Catholic in his year. Which would make him stand out to the other kids, even before he gets into arguments about why Greek myths are better than Christian ones, and would be obvious to all the parents and staff that he has SEN.
I wonder if the people complaining about non-practicing Catholics 'depriving' Catholic kids of places would complain about kids with EHCPs who do fulfil the admission criteria?
I decided against, because I predicted ds being in constant arguments with staff, and there was an excellent school he wanted to go to slightly further away. If however it was a Catholic school in my home town where only 2/3 the kids are from Catholic families and only half of them are practising (large Irish community the school was built for is much smaller now), then I'd have considered it if it was a good school.
Some Catholic schools do teach about contraception, abortion, other religions in a neutral way after the obligatory mention of the Church view. Others don't. Depends way more on the individual teachers than the religion of the school.