The biggest technical risk to Bitcoin has been, and remains to be, the continual growth of the UTXO set. As this continues to grow, under the current model, it will become less possible to run a Bitcoin node on low end hardware. This will inevitably lead to centralization if we don't take adequate action.

This is a true regardless of usage of OP_RETURN, Counterparty, Bitcoin Stamps, Inscriptions, Runes, Bare multisig outputs, but the aforementioned have exacerbated the problem bringing what would have been future concerns years out, into the relative present.