immunities was a better design than spike damage that PoE has
Both are shit mechanics. Only that you cannot avoid PI mobs in D2, whereas you can avoid getting oneshot in PoE, largely because there is no one-shot ability in the game that you cannot avoid.
It also had many better things like charging enemies (these were once dangerous in PoE as well), high damage but slow projectile enemies, teleporting enemies, raise dead enemies surrounded by swarming minions and the rest.
PoE has all of that. Rhoas/Vultures have a charge-attack, Necromancers and Devourers exist, and most of what you described exist as nemesis mods on every monster available. You may not notice them as much since PoE has a larger focus on bosses, and not trash-mobs, which is something I am personally hoping they will fix with 3.0. That doesn't mean all these different types of challenges on monsters don't exist.
I am arguing that PoE is more dependant on trading because of it's more layers of item modifiers that makes just looting items 99.9% useless (or you turn it into currency you use to buy stuff). I got few hundred hours of experience doing just that, no mere words can persuade me otherwise. It is like you are trying to tell me water is actually wine IRL, good luck with that.
How would you even know how much trading was required in D2 when you only played singleplayer and never tackled the actual endgame of either game? What are you comparing your PoE experience to? I'm not trying to sell you wine that is water, I'm trying to tell you that just because you were building sandcastles at the beach you are in fact not an expert architect. Of course you never needed to trade in D2. That's because clearing Hell Act5 was piss-easy and done in the first 24hours after a ladder reset. You didn't need to trade up until then, unless you wanted to PvP or do Uber-Tristram once Patch 1.11 got released. D2 is a game that struck an almost perfect balance between challenge and reward from start to finish, which is something no aRPG was able to duplicate. PoE is the closest we got, and it has 3 things that it massively improved upon compared to D2. Character customization, having an actual endgame and crafting. You don't seem to care or enjoy either of them.
Obviously a game that enables and encourages the player to experiment and enjoy the complexity and depth of its core-systems requires loot that doesn't limit this experience, but instead enhances it. Combined with the crafting-system the need for large amounts of loot to drop increases, which is why lootfilters are now a thing. If less loot dropped, people would complain all day about being unable to build their character the way they wanted, being forced to trade. It's more fun having a rather high chance to get the base-item I want to craft actually drop, compared to shopping Drognan/Larzuk for 6+hours just to get a decent base. Luckily this complaint is seen rather rarely, which directly contradicts your statement of trading being mandatory. So does the public outcry for SSF-mode that was just recently added. Now if we talk to people who actually engage with the end-game, then we have a different type of discussion and for those you generally do need to trade or grind, but this is absolutely no different to what happened in D2. And even then there are people out there killing shaper in SSF.
Also the game difficulty is around spike damage which is bad. 99% of the time you are murdering everything and suddenly you die, often with barely any warning.
Yes and no. D2 had more emphasis on white mobs, bosses were just loot-pinatas. PoE focuses on bosses the most. You are right in that PoE is balanced around the fact that instantly logging out is a possiblity, and therefore needs to have spikey damage so people can actually die in HC. However almost all of the deaths you see are absolutely 100% avoidable (disconnects excluded) by just playing differently, wihout logging out. The game lulls you in a sense of security, and when you do not pay attention something that is either extremely well telegraphed or is an affix on a mob/map that you can read kills you. Volatiles, Bearers, Slam-Attacks, Detonate Dead and other things are all very much avoidable, but since people are so set on trying to clear as quickly and as much as possible, they risk dying to these things. Sometimes the amount of stuff that can happen makes people forget about certain mechanics, and then they die to them. But in all the years I've been playing, I never felt like I died to something that was unfair, and I died plenty of stupid deaths. But in the end I as a player could've avoided it with either forethought, preparation or just not risking as much as I did. It's almost always on the player (unless your ISP/the servers fuck up). You dislike it, to me it's one of the things I like the most about PoE.
D2 is still one of the best aRPGs out there, especially when you play with some of the mods. I suggest taking a look at Path of Diablo or MedianXL, those might be the best mix of PoE/D2 and most to your liking. But please for the love of god stop talking about PoE as if you know what you're talking about, it is triggering me to hell and back, and back to hell again.