Opt-in RBF is a twist on Satoshi's original implementation of unconfirmed transaction replacement.
It is not imposed on any individual user and therefore is as much a contentious issue as multi-signature is, which is to say not at all.
Different variations of it have been discussed over the years and the current implementation has been reviewed, vetted & ACKED by a majority of the participants to the Bitcoin open-source repo.
Every single miner is free to opt out from this behaviour hence the outright stupidity of suggesting it requires miner consensus.
Go and do your homeworks will ya?