Great discussion, @McFluffin.
I think your 8 factors broadly covers it. My quick thoughts:
MultiPlayer - points discussed are mostly hygiene factors. I think more important to MP is the actual MP experience. For example, the current state of POE MP would satisfy the points you discussed. But not in my mind, because the average player wouldn’t touch POE MP with a ten foot pole.
Optimisation - duh. I expect unanimous agreement here 
Balance - agree. Nothing to add.
Trade - agree with your preliminary view of trade. I think aside from being a deterministic way to improve gears (thru accumulating resources to get rare gears needed), trade is what gives item intrinsic value. In a SSF world, an item is only valuable if it’s useful for a build you’re playing or a build you’re considering making (also to highlight the latter point is less relevant to players who like to minmax one/two “main builds”). And items being valuable is a core aspect of ARPGs for me.
Missed Opportunities - Agree. But re LE launching, I think one thing that also needs to be addressed at launch is ensuring the rewards to early access supporters are delivered. These are mostly the cosmetic fluff, sure. But EHG is almost sure to launch new support packs at release, and I think it would be terrible to have early access rewards still undelivered or in a bad state when they do so.
I haven’t spoken much of this because I agree it is more important to work on the core game before we get to the “fluff”. But just to highlight again, we need QoL such as permanently keeping our cosmetic pets out, cosmetic pets pathing logic is still non-existent (always converging into one), the kickstarter pets are of terrible quality (I was told they would be reworked), and basically to build in the cosmetic store to get the cosmetic armour and effects shopping going, etc.
Bland Mapping - Agree. Re POE comparison, the other reason why POE incentivise full clearing of map (until very very late game where some map rushing do happen), is that there is a cost to the maps. In LE, echoes are free to run so there is no real incentive to optimise the reward per echo, rather it’s all about rewards per hour (or any unit time we choose, the point being the number of echoes it takes doesn’t really factor into the equation).
Combat feel - This I definitely notice. I think this is something I automatically compares with POE. POE’s combat feels really punchy and ON POINT. Extremely satisfying when you pop monsters. LE combat really doesnt evoke that feeling or anything similar…
Seasonal content - Don’t disagree with your opinions but not something I am too worried about. heh 
PS: I have a very simple personal measure of Last Epoch succeeding. As part of my Epoch Kickstarter reward, I have unlimited access to the cosmetic store. If Last Epoch has a vibrant player community the day the amount of desirable mtx in store exceeds the value of my Epoch pack, that would be the day I consider Last Epoch successful beyond my dreams 