If everyone uses bitcoin to avoid taxes , what would the country be like without taxes?
It would be a free country.
There are alternatives for people who prefer to keep their privacy intact. The use of Bitcoin mixers is not the only way for a user to stay private. Having said this I think we really don't need Bitcoin mixers. We need ways to provide us privacy but Bitcoin mixers don't have the monopoly of this kind of service. The example given in the OP also provides privacy. CoinJoin also provides privacy in a manner that is legally acceptable. During these times when mixers are perceived negatively, there remains other ways to achieve what one can achieve with mixers.
Between mixers and airgapping a perfectly usable device to act as you wallet, mixing your cryptocurrencies is definitely going to be the more appealing option.
How is mixing a more appealing option than coinjoining? Mixing sites take custody of your Bitcoins and are trusted with your transaction history, but coinjoins are completely non custodial and do not leak data to any trusted third parties.