So, Mixers provide service of shuffling bitcoins or provide addresses loaded with bitcoins along with private keys. In short, they provide service so to create anonymity between sender's and receiver's address so that no one can trace the transaction.
My question is why not use Exchanges? When we deposit funds on exchange, bitcoins get deposited on exchange's cold wallet. But when we withdraw funds, withdraw gets processed from exchange's hot wallet. So in short, it is very easy to do anonymous transfer by depositing funds on exchange and withdrawing to other addresses. Why to pay 1-3% fees on Mixers when it could be done for much less on Exchanges. Exchanges like Binance charge just 0.0005 BTC to process withdrawals.
That won't work. Most exchanges ask for email addresses or worst, KYC. if you fill this up, you are already telling them your location so it won't work when you want to do anonymous transactions. Mixer is still a better choice. Well, decentralized exchange can be a choice too if that is what you are saying. I don't know much about the transaction process of decentralized exchange but they don't ask for KYC or email address. Just don't forget to use TOR or VPN.