IMO Amara could have been more compelling but that was never going to happen. First of all the showrunner who had started the Season left half way through and it shows. Second, this show just doesn't have the budget to put primordial beings into actual action. They can't even do archangels. Due to the changes midway through the Season, the people in charge clearly had no idea how to finish the myth-arc. On top of that the original plan was to kill God off and when the CW said no, they had to hastily rework the end of the Season. It was pure luck that Robbie wrote such a fantastic episode with 11x20.
It also didn't help that the show decided to humanize all these supernatural beings (Crowley, Lucifer, demonic and heavenly office workers) before we even got to S11. There were no more Yellow Eyes, Lilith, OriginalRecipe!Angels (Zachariah, Uriel, original!Cas) so there was no way they were going back to something like that with Amara. Amara can end the world with a snap, instead she kills only a few people here and there for the entire Season until the previous episode when she sends deadly smoke that kills a few thousand.
There should have been escalating destruction over the course of the Season because Amara's goal was a confrontation with God. She foolishly believed God cared about his creations so she started small (like the church massacre). Instead of her just sending a 'back off' ripple through Heaven, she should have destroyed it (because that's only logical). But since the showrunners weren't done with Heaven and needed it for the future, all we got was her shaking it up a little.
IMO the reason why they went back to Amara's connection with Dean over and over again to the point it became redundant and boring, was their clumsy way of avoiding what should actually be happening. Amara smashing up the planet on a larger scale the further we get into the Season. Then it would make sense that Metatron urged God to get involved (like lets say Amara had destroyed an entire continent) and that God was hiding. Instead she did less damage than Michael/Lucifer/Angels etc. even before they were about to have their super fight. Remember the tv reports of natural disasters all over the world getting worse the closer we got to the fight or Death about to wipe out Chicago before Dean came to him. Destruction was happening on a planetary scale.
Sadly there was no more talent left behind the scenes (aside from Robbie maybe) and supernatural beings had become a joke by this point.