There are other tools like Stowaway, which is like Payjoin, but requires interactivity of the sender and receiver. Payjoin requires the recipient to have a wallet on a server. Both complement each other perfectly.

We also have other tool like stonewall and stonewallx2. With STWx2, you collaborate with another user's utxos to make a payment to a third party.

I think a lot of people still think we're in a blacklist paradigm when we are rapidly moving to a whitelist paradigm.

In other words, if your coins aren't traceable back to KYC exchange, they are rejected. If you did a coinjoin, they are rejected. Despite our opinions about it, businesses are not obligated to treat sats as fungible.

As I said in the post about the Telegram Bot (#171665), most of the big players are afraid of using something that cannot be traced by chainanalysis precisely because they are afraid of not being able to verify whether the coins were or were not used for something illicit, and consequently being judged as interceptors of illicit money and paying court costs to prove their innocence. Now, it's interesting that small establishments don't care about this, because they are the ones who will usually benefit from not distinguishing the currencies they use.

The best part about payjoin is that its benefit has rough consensus as good for bitcoin unlike other privacy tools.

BIP 78 was designed with merchants in mind who have an always up http server. That means that no matter how many wallets implement the bip, the number of merchants is what limits the adoption.