I also don't trust the people who implemented it poorly to do it better in the future because I have every reason to believe that they implemented it the way they did because their primary concern was not the wellbeing of Norwegians. At every possible junction choices have been made which benefit immigrants and hurt Norwegians. If there was a more random pattern in the choices I would say that it could have been honest mistakes, but the pattern is not random, choices only ever go one way, and it's the way which has the worst outcome for Norwegians.
If we want to solve the problem of an ageing population we have to look to other solutions than mass immigration. One solution may be to give more tax breaks to working Norwegians who have children rather than giving their tax money to immigrants who don't work. Another may be to stop using public funds to indoctrinate the youth to view child-rearing as a net negative. And we could, of course, consider measures to reverse the damage that mass immigration has already done to Norway.
If the government said that you never have to pay income tax again if you have 5 children, then more people may have 5 children, this would be super low risk to try, much lower risk than mass immigration.