Look at the HDI: https://hdr.undp.org/data-center/human-development-index#/in...
Look at the top ten countries. How many are a constitutional monarchy? Which of them would you rather live in? :-)
There’s no discernible difference on this count between Finland and its Nordic peers that are constitutional monarchies.
https://govdata360.worldbank.org/indicators/hd8f5d509?indica...
I fail to see how making Finland more stable would improve anything, or that adding a monarch would achieve this goal.
Royalism sounds like the hunt for a silver bullet that would fix complex problems and institutions in a society. I don't think there is any evidence quasi-religion by itself improves institutions.