See here's the problem.
A middle way absolutely could work. James Gunn has proven this time after time after time. He's nailed in different settings with different characters. He's had his cake and eaten it. Which is why he's now King of the DCEU. But the main thing is, he proves your blanket assertion wrong. It is technically possible to go a middle way and win.
The trouble: nobody else is James Gunn.
(I mean, probably someone else is. Jessica Gao might be - not yet but she's on the way imo. But certainly 95% of Marvel writers aren't.)
And the secret to the middle way is simple - make the audience care about the characters and what they want, not bollocks like "SAVE EARTH!". But that's relatively hard for most writers to do. They like to write plot-heavy drivel full of kiss-off lines, rather than really building up characters you actually have feelings (positive or negative) about.
And yeah, expecting us to care about the destruction of Fictionalia just doesn't work unless we care about the characters, and they care.