I'm going to imagine anyone who needs to make fold-out leaflets is going to end up either doing it in Creative Cloud (i.e. InDesign), or these days, will just do it in Figma or Canva.

Microsoft abandoning Publisher is just another example of Microsoft's endless tactical retreats. Eventually, they aren't going to have anything other than Word and Excel (and maybe Outlook, but I'd say it looks iffy for that one).