The thing is, its even worse than this article implies: Monero's privacy doesn't even work in a Monero-only context either. There have been many researches done since 2018 that prove conclusively that it has always been easy/trivial to track Monero with just the info in the block chain.

For example, Monero used to make private transactions optional (ring size zero transactions). Due to the unique way in which Monero is constructed, having these zero ring transactions deanonymized the 5-7 ring ones as well. Then Monero had to make all transactions private by default to compensate. That bug was active for years though. Wired did an article about Monero exposing quite a lot about its privacy flaws:

Monero Privacy Protections Aren't as Strong as They Seem | WIRED https://www.wired.com/story/monero-privacy/

Aside from the bug I just mentioned, timing analyses allowed researchers to pinpoint the original spend coin with 90% accuracy, just using the blockchain. That was eventually patched, but as fluffypony says in the article, its never really going away. They raised the ring size in response, now its 16, but this still has like a 5% chance of working. Not to mention the newly released OSPEAD attack, which has worked since Monero began.

The guy who wrote about it said that it completely breaks user privacy and Monero's privacy would need to be redone. Its a form of statistical attack which completely unmasks users with just info from the blockchain. Its pretty wild. But the point is, don't have false hope, even in a Monero to Monero context, you don't gain any actual privacy. Coinjoin is always better because BTC doesn't have the same design flaws that Monero does.

Not to mention that Monero has an infinitely increasing supply with no cap, unlike BTC which is capped at 21 million. And hidden inflation bugs. Oh and did I mention that fluffypony was arrested for stealing $100k from his former employer 10 years ago in an office-space like invoice scam? Yeah, one of the founding members of the coin is a scammer...