Good summary.

> Bitcoin developers later introduced opcode "OP_RETURN", which is seen as a standard and less-evil way to post data.

This is not true and an error in the Mastering Bitcoin book. OP_RETURN was introduced by Satoshi in the very first version of bitcoin.

> Typically, nobody can afford to store more than a few hundred bytes.

This depends on the artificial constraints put on the network. Bottle operates on top of BSV which comes without a cap on supply and offers cheaper fees when compared to BTC.