I understand the concept of UTXO hygiene, but I'm not sure if these tools still offer real benefits now that exchanges, blockchain analytics, and surveillance techniques are way more advanced.
I would advise that if you are having much mixed feelings about using mixers, then you can use more privacy features in non-custodial wallets like coinjoin which would assemble UTXOs from different people and form a single transaction that spends back to another address in your wallet. You can do it more than once to improve the chances of your anonymity.
Coinjoin is a form of mixing. Whether the mixer is centralized or decentralized does not pose a difference in terms of whether an exchange will consider the coins high risk. Therefore, your advice does not provide any benefit. Actually a couple years ago there were complaints about this particular thing, people sending coins after coinjoin mixing and the exchanges blocked them.
I do not see the need spending back to a CEX when using privacy enhanced programs or features. since you want to maintain privacy, then it is important you make use of non-custodial wallets.
Whether someone needs to use a CEX or not is not for you to decide. There may be many reasons why users need to do this and we should let them. We can only provide them with relevant information and alternatives, they can decide for themselves. As of 2025, sending coins from a mixer, coinjoin or anything of this kind directly to a CEX is very risky.