The assumption here is that we want to stay in this Fiat to BTC on/off ramp paradigm forever. Plebs can mine monero profitably. If we're keeping the discussion honest, a pleb mineing Bitcoin is just some nerd with a hobby.

I would argue you need privacy by default if you really value it. BTC with coinjoin might come with little extra costs and work for your specific low level threat model nowadays but it comes with complex trade offs that might come back to bite you down the line, especially with advancing block chain...