I would do M+0, because Mythics are resurrection of that old pre LFD dungeons. They've appeared, because Blizzard really think, that LFD killed dungeons, while it actually revived them, cuz they were almost dead at moment, when LFD was released. Problem is - they wanted to sit on two chairs, i.e. prolong dungeons' life time, so they implemented timers and "infinite" difficulty ladder there. But this thing is what actually ruins Mythics for me. First of all I hate time runs. Back in old WotLK days I was doing dungeons for fun, not challenge. It was that "skip everything and get badges from last boss ASAP" crowd, that ruined dungeons and turned them into time runs. So, I guess, I would enjoy Mythics, only if I would play them with IRL friends. Yeah, I had IRL friends in this game back in old days. But they're no longer playing and I don't want to find new ones, because I don't want to put social obligations on me. Yeah, I don't want to be obligated to play this game, when I don't want to do it. And I don't want to be obligated to play with friends, when I want to do my own business.
But I agree, that the biggest problem with this game - is that Blizzard don't even try to find ways to solve problems with their game. Their game is way to "railed". They just say, that you have to play "this way" and that's it. You have to agree or quit. There is no room for "We have players with X demands and Y demands, that can contradict each other, so may be we'd implement some mode switch, that would allow us to satisfy them both". Currently it's something like "There is no game outside of M+ and raids", i.e. that old sweet "raid or die". Guys, who do M+ or raids automatically get enough gear and therefore character power to make everything else easy and therefore accessible for them. You do M+ for just 2 hours a day and hurr-durr you now have enough power to complete high Torghast floors. And guys, who do casual content, have to constantly struggle even with this causal content, because Blizzard tend to overtune it exactly to make it suitable for M+ guys. And casual content like Isle Expeditions and Torghast has major problem - you can't progress via this content itself. It always requires other kinds of contented as support.
Here is graph, that explains problem. Yeah, difficulty of some content like M+ increases, but not exponentially, so it's compensated but growth of character power. But not all content has growth of difficulty. Some content is trivialized by this character power. And more power you have - more easy content you can do. This is what is called "slippering from difficulty curve". And casuals have to climb on this difficulty curve first. Not all of them want to do it.