It might sound silly but if all they did were change the presentation so that meeting the timer isn’t the default expectation I think that would go a long way for making M+ feel less intimidating. So if you don’t meet the timer, the UI just looks like you just finished an M0. Nix the big red numbers and all of that. Make it like Baron timed runs where making time was actually a bonus.
That’s where this thread comes in. Why can’t one do both? Would it really be a loss if the currently near-pointless Heroic or M0 difficulties were put on a timerless sliding scale? Even if it rewards lower ilvls than M+, that’s fine as long as it’s sliding so running it doesn’t just fill your bag with scrapper fodder like normal, heroic, and (usually) M0 do.