The question is even, whether a coin, looking to serve privacy, needs to be "mass adopted". I would think it is better if not. Of course, you need some market cap for sure, but this is now largely sufficient for those needing to do private transactions amongst them I'd think. And honestly, if you can't handle a CLI, then maybe "private transactions on the internet" is not something you should consider in the first place.
Of course, an opposite argument is, the more people use it, the more "anonymity set" you get. But also the more attention you get, the more silly "demand for regulation" you get from disgruntled idiots using it not for matters of privacy, and, worst case, traders wanting it to be as regularized as possible in order for them to be able to use it as much in finance as a gamblers' token as they can.
As there is a steadily growing demand for privacy and the privacy of financial activities is an integral part of that, Monero could come handy. I do understand your concerns about idiots and demands for regulation,
but do you really want to surrender most of the market to DASH and Zcash because of them? BTW idiots, business folks, lawyers and their demands can be easily kept at bay as long as the devs and most of the community stick to their principles.
I have to say I don't know. On one hand, I'm tempted to say that too big a market is not a good thing, because it corrupts the basic ideas initially set out - look at how bitcoin is now a crabs bucket. If the thing is too big, grows too much, becomes a lucrative "investment" (greater-fool betting game), then essentially it becomes a toy for "idiots, business folks and lawyers". But I don't believe in the "devs and the community" either: I could just as well believe in state, people and government then, and if I do, I don't need crypto. So these are arguments to remain "small".
On the other hand, and especially in monetary affairs, small is often, dead, so that's an argument not to be left behind.
So, I don't know. I'm not very optimistic.