selective pruning makes you a bad relay. full nodes are the only real nodes.

putting data on the chain rarely is not an issue having big parasite protocols for storing data and gamifying is the issue.

letting them grow on the chain is the issue, narrowing rules never requires a hard fork.

core devs gets millions of funding its their job to be a cat.

if you close enough holes you make their job harder and harder, you change the rules under them, so they never grow, they can't, protocol doesn't like them, it breaks them constantly. they have to find bunch of weird tricks to put the data, make it more and more expensive, more and more complex, so its not worth it anymore.

best place to put spam is another chain, second best place is deep inside bitcoin hidden, worse place is out in the open in opreturn.