[plasticmachine]

Unsurprisingly, there exists research by the Monero Research Lab highlighting temporal association attacks and other possibilities.

https://lab.getmonero.org/pubs/MRL-0001.pdf https://lab.getmonero.org/pubs/MRL-0004.pdf

As to your last statement: even if the supposition is that the true signer is the most recent output on the blockchain, that is nothing but an unprovable supposition, which means that Monero enables plausible deniability at the very least.

Since transactions are both unlinkable (for any two outgoing transactions it is impossible to prove they were sent to the same person) and untraceable (for each incoming transaction all possible senders are equiprobable) the anonymityset continues to grow, which makes the privacy risk cryptographically negligible.