For disadvantages, how serious are they, how easy are they to be abused, to creep into the codebase, to be prevented from happening again, etc.

It also depends on the team. If it is a small team of 5 people and they are all excellent engineers, I think whatever languages are fine. The 5 engineers will discuss and decide what features to NOT use, etc. and abide to them. If it is a team of 500 engineers, it will take much more efforts and eductions and much longer to achieve that.

Lambdas, First class functions, and closures are a great feature missing in basically every other popular language (things like Javas lambdas or function pointers aren't even close in real world use).

Proper tail calls is another feature missing from that list and despite some browsers refusing to honor the spec they ratified, it's still implemented in Safari/javascriptCore, XS6, duktape, node 6-7, etc.

The interplay between js dynamic objects and closures is difficult to describe, but a thing of beauty when fully understood. Object literals are also basically unique to js on that list as well.

There's a lot to love about most languages and JS is no exception.