For me it's mostly traditional, but I would actually love more complexity on certain aspects that were clearly designed for human math ease-of-use. So:
Actions - Traditional
Reactions - Traditional
Dice Rolls & Modifiers - More Complexity Please
Traditional power of weapons and spells - More Complexity Please
For the items that I want more complexity - what I would love to expand on is have more nuance instead of just "advantage/disadvantage", and resistance or no resistance - a lot of the 5E elements that purely designed for easy math at the table, but IMO feels a bit simplified for a computer game.
For example - fire resistance being a flat 50% and immunity being a 100% feels very simplistic and not very immersive. Would love to see smaller increments so you can differentiate enemies more, or even encourage various types of item stacking (like in BG1/2)
Another example that I think Larian has NOW done well is high ground. The +2/-2 flat modifier for being on higher ground is 100% not RAW, but I much prefer that to nothing (less tactical depth), or advantage (too much, too redundant).
