You do have a few options in the early game. (I will avoid discussing options at level 10 or higher)
First, all Rogues have the Surprise Attack ability, which makes their foes flat-footed for the first round of combat (though you do need to beat their initiative).
Assuming you have some melee combatants in your party, consider strategizing with them to ...
The best I could come up with is 2,084 damage.
Use an Oathbow (1d8+3d6)
Drink a Potion of Giant Size from SKT (Oathbow now deals 3d8+9d6)
Use an Arrow of Slaying (+6d10)
Have Dexterity 20 then use Dex Tome (+6 dmg)
Paladin 3 - use Branding Smite (+2d6) also gives you Martial Prof to
use the Oathbow
Rogue Assassin 17 - get "Assassinate" "Death Strike" and ...
"When you cast a spell that requires you to make an attack roll, the spell’s range is doubled."
Notice that this doesn't specify ranged attack rolls: don't forget there are several melee spells that require you to make a melee spell attack roll on something within 5 feet of you, instead of at touch range. So if you have spell sniper, this doubles to 10 feet....
Ranged attack within 5' is at disadvantage.
TL;DR Your interpretation is correct. The attack is at disadvantage.
Ranged attack in close combat at disadvantage
The Revived Rogue published as Unearthed Arcana gets a ranged attack inflicting necrotic damage, which is going to be an issue for shooting while opponents are immediately next to a character.
And that's really all the game cares about. How you wish the fluff it is up to you and your DM, but as far as the game is concerned, you use a maneuver, it causes the enemy to go flying back 15 feet if they fail a strength saving throw, and that's that.
You could fluff it by aiming higher than the center of gravity or something, or perhaps it's a "...