There's no such thing as citizenship of convenience.
If someone becomes a Canadian citizen and then leaves Canada (whether a few days or a year or 10 years after becoming a citizen), he/she will:
1. Have to turn in OHIP or equivalent in other provinces (not entitled to use public healthcare)
2. Report his non-resident status to the CRA
If he/she then returns, then these are the scenarios:
1. He/she returns with his/her family and are low, working, or middle-class individuals: Then they will need to have a job especially in expensive cities like Toronto and Vancouver; they won't come back if they didn't secure a job. This means they will pay income tax and tax on whatever savings they have. As taxpaying citizens they will be entitled to use OHIP, send their children to public schools (or borrow etc if they want to go private). This cannot be objectionable to anyone even some of the elements in this forum.
2. He/she returns with his/her family and are upper middle-class or upper class individuals: Then they are reasonably well-off that they won't leech off the system. Such people are more likely to send their children to private schools, to top universities rather than Canadian ones, and wouldn't need torontosm or the other person's money. Eventually, they will have to supplement their income either through starting their own business or finding a job.
Any which way you look at it, nobody will just leave Canada for no reason after getting citizenship, stay overseas, and then come back merely to leech off the system: they will need to have income to pay for university. As for healthcare and education, they will have to either be very rich or have a job or business that generates income in order to keep living here, especially with everything becoming more expensive each and every year.
There's no scenario in which a family would just come in to leech off resident taxpayers, and given how tough the CRA is, they can't even lie about their residency status when they're back as they'll need to get their OHIP cards back if in Ontario and need to prove their status everytime they apply for any public services. Feel sorry for the nutters on the opposite side of the debate.