"IF" I would have conducted any coin activity this year it would have been on segregated wallets because
Even so, "if" you sent a single transaction, regardless of what wallet it was part of or even if it was just a transaction to yourself, the IRS would expect you to answer yes to that question.
There are hundreds of small transactions in my main wallet and I guess if the tax authorities go after the Bitcoin users, then I probably need to move my coins to a fresh wallet using a good Bitcoin mixer.
This may or may not help you. If the addresses in your main wallet are already linked to your real details, as they would be if the coins have come from an exchange you have completed KYC on, then mixing them doesn't really help. The IRS will still know that you owned x amount of coins. The question won't be "Do you own crypto?" but rather "What have you done with all the crypto we know you bought?"
But is it even practical for the tax authorities to go after millions of Bitcoin wallets? They may be able to trace a few of them to individuals. But is it going to be worth the time and effort?
Yeah, they can't investigate everyone, but they will go for the low hanging fruit, primarily people who have completed KYC on large exchanges which freely hand over data to the IRS.
Sticking with my "IF" qualifier here; --- "If" a US citizen had some reasonable BTC from long ago and it was entirely acquired without any KYC/AML and was kept fully anonymously in unique wallets it would be untraceable if the connection issues were all handled well. Then "if" that user had made 2020 transactions/exchanges but they are small by overall standards to the total holdings, that user could decide that if need be those coins would be forever lost in the blockchain effectively disappearing from his/her/their possession. Such a user could decide that they would rather surrender/lose those coins than answer YES on a tax form. Effectively kicking the can down the road for a future decision not fully knowing the consequences of answering YES. At some point in the future those lost coins could be found again given a proper circumstance. "If" I were in that position and if I was a US citizen that would be a very tough call to make.