A non-KYC exchanger that uses third party exchanges to process transactions could very well be a good alternative to a mixer.
If executed well, it can be very hard to detect the transaction has gone through the exchanger service. Now for instance binance.com allows users to create new deposit addresses for each deposit, and I assume this can also be done via API. So not only is Binance supporting these services, it's even enabling them. So long as big exchanges tolerate such services they're gonna function.
You're still going with the mixer narrative, but you're wrong. Binance keeps track of every transaction anyone ever made, and so do most other exchanges. They're a lot like banks when it comes to keeping transaction records. The same goes for casinos.
If you're trying to hide your payment from your wife, then depositing and withdrawing to an exchange works very well. If you're trying to hide it from a government, they'll probably find it if they start looking. And if they automate everything and check everything, they'll find everything. Now that I think about it: I'd be surprised if chain analysis companies don't have access to this data already.
The thing here is, so long as your name is not attached to a transaction, it's hard to track.
BTC mixers also operated much like centralized clearing houses. It was obvious to third parties seeing the transactions to associate your coins with the mixer. So in a way, these coins were even more "tainted" than having to pass through an exchange.
If you use an exchanger to pass your coins through an exchanger, the pot they get mixed in is actually even bigger and much if not the majority of this money is from "clean" transactions so it's hard to be labeled as "tainted".
And to clarify, given that exchangers don't collect any user's identifying information, with some even operating via TOR, nobody cares if the underlying infrastructure utilizes Binance. With the right use of APIs and fresh addresses the exchanger can make it seem like the coins came straight through the exchange, but because of the exchanger the only name attached to these transactions will be the KYC'd account of the business owner. So if the authorities crack down on such service, they'd see hundreds of thousands of transactions with the name of one party, going to hundreds of thousands of different addresses. By all accounts, this acts like a mixer because it negates KYC/AML measures and makes transactions much harder to track from point of entry to point of exit from the exchanger.
Think about it, not it's not just BTC inputs and BTC outputs. It's coin x to coin y and potentially even from chan z to chain u... So going through any metadata to decipher the flow of funds become even more complicated unless they seize the data of the exchanger. Depending on implementation also, some exchanger transactions might also be completed without any transactions on the exchange, by utilizing own balances. Of course this is a matter of trust and an exchanger utilizing nothing else than the API of a centralized exchange would be easier to track. And given how opaque these services are it's hard to know what each one is doing.
I wanted to add with an edit of something I stumbled upon just after I clicked away from this thread: through
this mixer review you will see that most of today's functioning BTC mixers will themselves shove out exchange coins which are considered "clean" among the crown that feels the need to use mixers. So the no-KYC exchanger is a very likely replacement for a mixing, especially given if mixers do the exact same.