Citrea doesn't depend on Op_return, they can use use unspendable taproot outputs instead and bloat the UTXO set, I think that's actually how it's currently implemented but haven't checked.

You'll care about miners if there's only one or two big ones that no one can compete with and the State can just hijack to mine empty blocks.

Bring able to estimate fees correctly is also pretty important.

And aside from all this, if people actually wanted a viable alternative to Core and weren't just mindlessly following a renegade cult because it makes them feel good then they'd use libbitcoin not knots.