Does Bitcoin + mixers = Monero? Moneropedia defines &quot;ring signatures&quot; as:

Ring signatures make sure individual transaction outputs on the blockchain can’t be traced. A ring signature is a group of cryptographic signatures with at least one real participant, but there is no way to tell which in the group is the real one as they all appear valid, while the key image prevents double spends. When sending a transaction, you select some random transaction outputs on the blockchain and mix those with your own “real coins”. Mixing of coins is enforced across the network, making all coins “equal”. Because every transaction output has plausible deniability on their state (spent or unspent), there are no fungibility issues with monero
To read how Monero gives you a privacy by default (unlinkability), see stealth addresses.
A group of cryptographic signatures with at least one real participant, but no way to tell which in the group is the real one as they all appear valid.

It sounds like Moreo's ring signatures are basically a way of building mixing right in. So, is Monero effectively the same as Bitcoin+mixers?
No. Monero's ring signatures draw on Monero's complete TXO set to create a larger anonymity set.

Monero's method has the disadvantage that since it is unclear which TXO were actually spent, they can never be marked as spent and therefore spent TXO  hardly ever leave the TXO set.

In Bitcoin mixers, you're actually dependent on other users also using the same mixer.