Angular is pretty good. But it likes to own the page, if not the whole website. It is hard to,
a) Have Angular co-exist with other stacks
b) Inject angular for one small quick job
c) Package an angular “widget” for use in wordpress, sharepoint, etc.
Interestingly, this is something AngularJS used to be able to do, but Angular has sort of lost this on its way. Technically all of the above is possible with Angular, but it’s complex. Very complex.
And this is exactly the gap that Angular Elements fulfills.