Is/Was prohibited anyway in Switzerland, so this vote didn't change anything on that fact. Though this argument has been used during the campaign before the vote.
I do agree however, that things like minarets should better be left to a general building code addressing the problem of architectural shouting contests without explicitly mentioning religion. The stupidity of having the literal phrase (well, in german) "it is forbidden to erect minarets" in the constitution should serve as a warning to anyone who praises direct democracy all too blindly.
I really don't get it why cases like that are solved with a polar vote (change or no change), not with approval voting offering more than two possible results on different levels of compromise. There seems to be a tiny glimse of it (only on the wiki in german: https://de.wikipedia.org/wiki/Doppeltes_Ja_mit_Stichfrage ) but that is just three way between no change, proposal and one administrative counter-proposal, which still leaves the door wide open to polarism.
When you hire for a company you want your dream team to have a diverse background of ideas and experiences but that doesn't mean you let them work on the goals and products they worked on at their previous employer with whatever processes they want.
Edit: to be clear, I'm not sure the specific minaret law is a downside from my experience, but that is not to say that your overall point on populist reforms is invalid. I was just focusing on the specific law.