When teaching, shouldn’t you just tell the students which packages to use and be opinionated about it yourself? If a student chooses to step out of the list you provide, the onus is on them to justify their choice. More generally, you may find my 2 comments here relevant. Personally, I can see that the “problem” exists but I also think that the solution from a user’s point-of-view is to have more people like yourself become opinionated about their favourite packages when teaching or using Julia. Then the most popular packages among teachers and package developers will naturally emerge as the de-facto standard.
I think we are discussing 2 related problems here. First is the problem of new user confusion which can be “fixed” by opinionated teachers. Second is the problem of resource scattering which can be “fixed” by more communication among people of similar interests. Whether this is done at package registration time or at conferences and meetups is an “implementation detail”. We just need to talk more to each other one way or another.