Sam makes sense as Steve's replacement -- Captain America is about an "ideal", not a set of powers (or a skin color).
Miles Morales and Kamala Khan (and Sam and Rhodey and She-Hulk and X-23 and Captain Marvel and the new "Thor", etc, etc, etc) are not "pushing" anyone aside. They were usually inspired by the "original" heroes to take on a superhero persona in their honor and -- more importantly -- the original characters are often left intact in their own separate series or return to the series after a short (and often beneficial) hiatus.
What you seem to be fighting against is more about principle than anything really tangible, especially given your criticism of my opinion regarding titles like "Ms. Marvel" and "Spiderman 2099" being good comic books that are worth reading, dismissing them instead as just "pandering" regardless of their content.
Again, if you don't like these books (or said "diversity") that is fine but it really makes no sense to criticize those of us that do for having our own opinion on on the matter; no one is forcing you to buy these books any more than anyone is forcing me to buy the 3 or 4 "original" Spiderman titles over one about Miles Morales.