It's not only the song writing.
The melodic rock 'sound' itself has become too formulaic. We need some originality. We need some guitarists who haven't learned all they know from copying Guitar Magazine tabs and Youtube. Singers who aren't all trying to be exact Steve Perry or Lou Gramm clones. Producers who can capture the human touch instead of the perfectly tweaked, filtered, over-processed cut and paste producing that seems to be the benchmark for this scene these days.
Imagine if a perfectly good CD came out with great songs but an unknown Ritchie Blackmore or Mark Knopfler as the guitarist. People would probably say "it would be a great CD if only they had a decent guitar player"! People seem happy to hear slight re-arrangements of the same 10 or so songs over and over again.

Unfortunately I don't think the target audience in the main is open minded enough for anything to change. There's no appetite for pushing the boundaries too much. The parameters for what constitutes AOR/Melrock today are too narrow. Which is probably why I am listening to less and less of the bands discussed on here.
Some of my favourite melodic rock albums of the last 15 years have been the more daring ones. Harem Scarem with Overload, Toto's Falling In Between, Europe's Start From The Dark, etc.