The Forgotten Realms isn't about always having a heroic narrative. It is about making choices that influence whether you and your group will be heroes or villains. This is why players can choose their character alignment in most games. You don't gotta play the hero.
Well I will always play the hero and I liked that the BG series took this aspect of the FR setting. To my mind the FR setting was set up as an alternative to the grim-dark of Greyhawk / Oerth in which neutral was the default. The primary motivation behind a Greyhawk adventure is greed. Let's gets those golds from the dark crypt!
By comparison to Greyhawk the Realms are:
Finally, the Realms are a land of adventure, and therefore adventurers. It is the time of heroes, when one man of pure heart (or with a powerful artifact) may hold his own against enemy hordes, where legions of evil forces may muster and be destroyed by the actions of a few, where the nations rise and fall on magical tides which mere men can control. It is a time when the bold and the lucky may make their fortunes and gain great power over their worlds.
(If could upload photos from my computer I'd give a screenshot of the page)
Destroying evil hordes, pushing back the forces of evil.
I also don't quite get how you took away you couldn't be heroic? I am doing a good guy run right now and I feel pretty strongly in my character and his righteous conviction as he made choices that actively put off his obtaining a cure to help people in need. All the while keeping a deadly poison on his person he planned to drink if it came to it.
I felt pretty heroic. Was there anything specific that made you not feel that way?
Nice!

I also liked saving the Grove and disrupting the Absolute's plans. But so far the tension in BG3 comes from self preservation. As the Thayan door acknowledges -- self interest is a Thayan value. Compare this to the tension in BG1 -- 1) end the iron crisis and 2) stop the war with Amn. BG2 -- rescue your friend before it's too late and stop the evil mage from becoming a new evil god. (and, yes, the alternative to see these as revenge and self preservation missions).
Now there is still an opportunity for the narrative to shift from exclusively self interested to heroic. Stopping the evil before it hurts others instead ending my personal crisis would make it feel more heroic and 'realmsy'.