Everybody knows that Monero is claimed to be the only anonymous coin, but even it can't guarantee complete privacy. For example, if there was not enough time (less than 20 minutes) between your transactions of buying and selling, your wallet can be revealed.
Personally I don't use Monero, because now I don't really need a lot of privacy, I don't need to hide or launder my money.
Sure, you can apply all kinds of different statistical parameters to detect connections between wallets. Output sizes and so on, but as you say timing is very relevant, but that also applies to mixers for Ethereum or Bitcoin. That is why mixing service providers usually recommend to wait even up to 24 hours if possible. I guess that is where many users think that they can go for shortcuts and 3 hours are also fine, but it is in fact not. You really need to be a patient individual to ensure that you've put the most effort possible into keeping your actions on the blockchain private.