Nah, these are broad strokes you are painting with. Sure some of them needlessly reinvent, but some back end people needlessly reinvent databases and API basics.
But my experience is not the same. It has always been others telling the front-end devs what we "need" to have. I am constantly pushing back with "buttons and links should look and act like buttons and links", "right clicks don't belong in CRUD apps", and "we have a select component that does that". But _BUSINESSES_ want their identity and unique perspective baked into the app.
There is similar reinventing trends movement also in the backend universe.
For example, there is a fashion [1] to include hashes in the names of static assets served. But that's what ETag header is invented for, in the RFC since a decade and implemented in all browsers.
[1] (I deliberately call it a fashion, not a standard; would rather say that RFC 7232 is a standard in this particular case)
It's the boot camp point I think, over-represented in FE (but I haven't done a survey and not GP, just my impression) perhaps because it's more tangible/accessible - 'oh yeah I'll learn to make websites'.
Or perhaps just that it skews young, which I could believe, and might be easier to find survey data on.