In the case of stepping up into the "Big Leagues" and trying to capture a bigger fan base, then you may have to polish the engine, expand the scope of your story telling, and make a bigger sandbox. The aspects I will mention could also be added to your current adventure as a DLC to help re-play value of the main campaign.
By "polishing the engine", I refer to the character graphics and customization. The ability to customize and identify with the character is very important to many people and many mods are dedicated to appearance and clothing in other games. I was content in finding four faces that went with Male and Female voices 1 and 2 for a two male two female party. For male one I made him look like Ragnar from the vikings, with a long beard (auburn in color..looks the most passable), and male two was a face and hair that made him look like he was in his upper 30s and that fit the voice.The females were definitely harder to make presentable, but playing with the colors helped make the hair textures look a little less plastic.
Honestly, I don't know what is the most cost effective way to improve this aspect. Sliders perhaps or more face choices. Something to create the illusion of higher resolution hair (especially around the face...the backs look OK). and two-tone options maybe? More armor color customization. Accessories like tabards, that include the ability to choose a custom logo and a way to easily drop customized logos into a "logos folder" (no modding necessary...the choices are immediately recognized).
Far objects look amazing in your game during close ups, you can see the trees blowing in the night sky for example :). Star trek online is a older title that has dated graphics, yet you can still make a "space Barbie" ...or Ken (implied, although men are always easier)...that look awesome. The clothing customization makes it easy to make a unique look. Free download if you want to check it out. I don't hear any of your current customers complaining, but to make bigger titles you will need to draw more people in. I noticed this a minor immersion problem, as I prepare for a second play-through (just purchased call of the wild). It feels like I am just playing the same party in different classes.
This leads me to the last two points, which go hand in hand: Opening up the sandbox and creating more non-linear story telling.
*Pause* I feel so bad for Larian. They had a great idea and screwed themselves over by F***ing it up...like, completely! Their vision of origin characters, that are fully voiced, with thousands upon thousands of lines of dialog was a home-run idea! Ooooops! The characters are crap!
Gale is the best character by far (story-wise), but is a meme for the corpse you drag around. This, because ranged characters (that you want to keep away from the front lines) have NO range (Wiskey, Tango, Foxtrot!). That and he is a Xorn that wants to eat all of my magical items...erm, so he wont be in my party.
Wyll is my best companion, tactically, and the second best personality...coming in at passable.
Astarian is decent in combat, but is the tag along companion we get to dig the latrine at night...gone at the first chance.
Lae'zel is the poster child for this story and is very good tactically. Her personality is grating, but in character with race and backstory...she is in,
Shadowhart: Crap and uhm really crap!
The Tiefling female that they have planed to be an option...rude crude and nasty.
The shame is all the wasted hours of time and money to get it wrong.
Your characters were likeable...ie polite, in character with the medieval theme, but not overly dramatic. They were caring, but not excessively emotional...like the bard tiefling in BG3 who is supposed to move me but just fails...can't completely put my finger on why either...go figure...Larian messed her up too.
The point is, its a big investment to open up dialogue options, so I would get some kind of feedback on character selection before committing to new ones.
If you were to consider doing a fully licensed story, either your own in the Faerun realm, or a classic story, then you will need to invest more time in the story and options. You have proven engine, and implementing the official rules would be cake. Again I have confidence in your team based on the story you did.
I would go with something that includes at classic familiar elements. Strahd, Elminster, Drizzt, and others are Iconic and will definitely draw a crowd, however their are many areas, such as the Moonshae Isles, that have untapped potential for an Iconic story, especially if you set your story farther back in history.
There are unique race of elves called Eladrin and human race called the Ffolk and of course all the classics.. Moon wells that lead to the Feywild...great if you want to set up an adventure that succeeds in great sequel potential. The Feywild is a great place to challenge high level 5e characters, and has many mythical races and beasts...the stuff that "fairy tales" are made of in places like Balder's Gate and Waterdeep.
Go Big, but Do your homework!