If I am not wrong, the advantage of using a trustable Mixer is to save time secure your assets, and pay a lot lower fee as compared to what you will be paying for swapping Bitcoin to XMR and then XMR to Bitcoin after receiving it on the other end.
Could be a lot lower fee. Could be not.
Swapping Bitcoin to Monero is some times cheaper. You have some Instant Swap Centralized Exchanges asking for 0.5 percent fee. For small to moderate amounts of Bitcoin swapped, that is pretty decent. I have seen some Mixers ask for absurd fees before.
It is also possible to swap to Monero and after the swap Bitcoin price decreases, Monero price increases. It could balance the amount you lost on Fees or even earn you more. Of course. The opposite can happen any time too.
Point is. Do not choose convenience. Choose what is more important to you. Using Closed Source or Open Source. Finding a Decentralized or Centralized way to go. There are options, still.
If you want to keep it in XMR, you can go with that but it's not really efficient if compared with mixer service and the ease of it's use as you do not have to install any software but that comes with a lack of privacy to be honest.
What are you even talking about. Monero is the only Cryptocurrency offering Privacy for pretty much any body. Even for the less technically expert people.
You think ease of use means more Privacy? The official Monero Wallet is fully Open Source. Mixers are not. This makes Monero a MUCH better alternative if we compare Closed vs Open Source.