The minimum fee is currently around $93 per MB, and can easily go up to $10,000 or more. It doesn't matter if many people are against if or not, anyone who wants to use OP_RETURN can do it already.

Proposing changes to Bitcoin Core needs community support, and if most people already don't need the changes you're proposing, it doesn't make sense to add it.
It makes perfect sense to store a hash to proof certain data existed at a certain moment. Why would you want to store more? And what kind of data would you want to store in the blockchain that can't be stored any other (better!) way?