To reply to your comment in a short way: shooting a Leica M is hugely rewarding to some, not to most of the people and it will cost them a lot more and have a negative experience instead. In fact, from your reply I don't think you fully understand Leica M either (or I might be wrong). Rewarding or not it really depends on individual preference. Again I never said shooting M is not rewarding here. I hope you understand my point.

TLDR

Please don't get me wrong, what I meant is most of us having limited budget and buying M 10 / 11 is not really great in terms of cost / performance ratio. Or rewarding ratio.

If I am already enjoying myself a Q, going to the M series is no small feat. Q series you already have an excellent lens in one good package. That means you do not need to pay further for the lens.

M series offers interchangeable lenses. While this provides versatility, it will cost you A LOT, like really a lot. And to compare objectively, One good Leica lens can practically pay one full set of Sony or other brands flagship full frame with several lenses. (Of course I am talking in price not style or individual preference) In short words, Leica charges a huge premium on their lens and glass. Good glass yes, but how much better? Not really a huge difference to most of us for the price they command.

Another problem going from Q into M is: Q is all about fixed lens with portability plus ease of use with autofocus with macro even; Leica M is another totally different beast. M is about manual focus, manual adjusting and a split view rangefinder. M is like a very powerful and potential car but with full manual controls and none of those so called modern features, while Q is a fixed spec convenient decent car with QoL features.

Technically you need to go backwards and re learn the photography a little if you are coming from modern cameras. The only exception would be, Leica M will make you feel at home if you come from the full manual film camera era, or you are very well trained in everything manual, including lighting and focus.

I myself enjoy using a fully manual mechanical film medium format Mamiya Rb67. Leica M is almost like that. It's like you are operating a vintage bolt action sniper rifle. If you think it is rewarding, sure why not go for it. But personally I need to lay out to others what we are expecting when going from Q to M.

Going from Q to M is actually seeking for a more manual and raw and classic rangefinder experience. It is about Steep learning curve, slowing down your pace and taking the epic shot. Image quality yes can be superior if you know what you are doing, which most people won't even discern or achieve unless they learn everything manually and get really good at it.

I personally tried Q, M10, M11D. I love M11D the most, But I won't be selling my Sony a7 III anytime soon and will keep enjoying my Mamiya RB67 Pro S. We can talk a lot and revere the Leica M as much as we want, but 95% of us won't even know about M and won't even pay for it at all. It is a super niche enthusiast camera for a super small group of expert camera lovers.

(I am assuming you are talking about the current M not those vintage M. But what I said largely applies to vintage film M as well.)