For what it's worth...
1) Increasingly in gaming I'm looking for games that are playable in anything from 10 minutes to a few hours, but with a meta-game or long-term unlocks that keep me coming back. I'm loving Renowned Explorers, for example, which has some hard and definite constraints - each game is 5 expeditions only and will take max 3 hours to play through - combined with a feeling of endless replayability, which comes essentially from the endless possible combinations of characters (choose 3 for each game, out of 28 available - and each of the 28 has a very unique personality and traits!)
2) Zombasite in my experienced started to fall into a Paradox games-trap: too many systems, interacting poorly, without a strong unifying game dynamic. An ARPG combined with a diplomatic / town-builder dynamic that started to approach EUIV in its complexity - but it was all spread too thin, and in the end I found neither the ARPG elements nor the town-building satisfying. I'd strongly recommend paring back your game design to the essential elements, and then make sure those essential elements are work together smoothly and all contribute to a strong design. It's like women's fashion advice - put on everything you want to, then take off 1 thing and you're ready.
3) I can see real potential in a stripped-back dungeon crawler with a definite hard constraint on the end game. So something like 10 dungeons, total 10 hours play for a given game. But there is infinite replayablity through character class recombinations, and a strong metagame with lots of unlocks and ongoing goals to keep working towards. And within game, experiment with a simple system of upgrades aside from the usual XP->level up and loot dynamics. For instance, how about you're gathering crystals and lugnuts while exploring, and crystals and lugnuts can be spent in town on meaningful town upgrades, with real consequences for town development this way or that? No micromanagement of town stuff, just invest those crystals into buying a strong defensive wizard, or improving happiness by +50% for everybody - but you can't do both!
4) Graphics. I'd love to say I don't care, that it's all about gameplay. To some extent that was true for Din's Curse, where the graphics were relatively minimal in the dungeons, and smooth animations sorta made up for it. But it's not true in Zombasite - the graphic design I feel really gets in the way of the game. Don't aim for Diablo iii-esque graphics if you haven't got a team of 100 artists to make it work. Instead, strip it all back to a unified minimalistic theme. Renowned explorers, Desktop Dungeons, Darkest Dungeon, heck even mini metro are all good examples of smooth and effective graphic design on low budget.
5) The emergent dungeon phenomena in Din's Curse were revolutionary at the time, and have been picked up and further developed in other rogue-likes and even standard RPGs. Divinity series is a good example of combat craziness due to the number of different substances / spells etc that can interact with each other. So amp it up! I want to see mold, smoke, pools of blood, piles of rubbish, explosive powder, sheets of metal, underground rivers, acid, ether, mana clouds, dead magic, etc all swimming about together in the dungeon. So I can go: "hmm, if I vaporize that mana crystal with a lightining bolt, I can use my gust of wind to blow the ensuing mana cloud into that room over there that is full of conductive rods... then I'll lure the boss into the room, activate the rods and quickly shut the door. Problem solved!"