So... it's not just me, then?
My motto is now and always has been: "Learn the rules so well, you can break them in your sleep."
Spell-check is always useful, but in the end, as far as crafting sentences goes, there's no shortcut. You gotta (yes, I intended to write "gotta") know how to do things the hand-crafted way so that you can determine how correct the app is when it attempts to correct you.
Put another way, if you don't know the difference between "discrete" and "discreet" to begin with, your chances of a direct hit are still only 50-50.
But most delightfully ironic to me is the thought of handing over decisions about good English writing to an app that calls itself "Grammarly."
Seriously?
Almost as unintentionally hilarious as those emails whose subject lines promise to teach me how to write "web copy that doesn't SUCK."
DR