Gotcha. What I don't understand is why the UX is so bad. In all the wallets I use, RBF is enabled by default, I don't have to think about it, ever. If I wanted to use a service that would like me to disable RBF for a transaction, I could decide to do it if I see fit. There's definitely room for improvement, but the UX of a wallet where Opt-in is on by default seems the same to me as one with Full-RBF, with the added benefit of signalling intent to (potentially) replace the transaction.

You don't have to "plan your mistake", just leave Opt-in RBF enabled and you don't need to think about it.

So I'm guessing your point is that today users kind of need to understand what RBF is to be able to pick a wallet that allows them to benefit from the comfort of RBF most of the time (thanks to Opt-In RBF being enabled by default) while still signalling and being able to switch the feature on and of. As I've said in another comment, this could be made largely easier by communicating that RBF should be disabled for a specific transaction throught a BIP0021 QR code, letting the wallet automatically disable it just for this transaction and automatically reenable it after, keeping RBF the default.