I played the demo and really enjoyed it, had a great time. Here's my main critiques:
1) More variety in backgrounds. It would've been good to see a background like the outlander/hermit from the PHB, as I found it a little difficult to remake some characters without a background that suggested the idea of someone living in a secluded society or in the wilderness. Obviously the game should have backgrounds that work with the lore + setting, but I thought having academic and philosopher was a bit redundant, even if they did offer different proficiencies.
2) Something to do with our custom characters! Just being able to level them so we can experience the levelling system and subclasses would have been good, or having like a mini-arena to test them out in combat? Apart from that I was really impressed with the character creator.
3) The spider fight at the end felt a little too easy. Maybe it's because the pre-made party had two casters with light, but the big spider fight wasn't as difficult as I anticipated. The fighter and cleric got left behind and were able to fend off the spiders pretty well, and I never took a long rest. So, something to consider.
4) Using Detect Magic and Identify felt a little unnecessary. It didn't make a lot of sense to me that the party would pick up an item that had an unknown property, and wouldn't jump straight to Identify.
Apart from those 4 things, I thought the demo was great! I hope you have a good time developing the rest of the game!