1) On PC or console? On PC I recall nearly every game having a quicksave/ quick load key bind even before Souls games. On console there’s been auto save for generations, but usually only at certain very specific and limited points. Unless you have specific examples otherwise?
2) It’s still largely unique regardless of knock-off games using it. Also the message system can add a new dynamic depending on the players’ intentions in creating them.
3) Metroidvanias have maps that are permanent resources once you cover the ground initially.
4) Fair enough, but also hardly a mainstream idea which is why it was thought of as a big deal with Demons Souls and the other games.
5) What I mean is the player themselves has to seek out the game’s larger story, lore, etc. by interacting with everything or person they find vs a cutscene just spoon feeding the player everything for merely reaching checkpoints, level requirements, etc.
6) Yeah, it’s not particularly deep or skill-heavy, but next to most mainstream games in similar genres where you’re able to button mash or hack away with reckless abandon, you’ll die very quickly in Souls to even scrub enemies.
Having said that, it’s ultimately in the eye of the beholder. Although even when solely using the broader gaming community’s response to the series as a metric it’s safe to say it scratched an itch most people either didn’t know they had, or had for whatever reason missed.
Iron Man mode (which is to say, you can only save/load by quitting/opening the game) as I said was a common enough option. Yes an option, but I don't think it beign enforced is necessarily great either for a host of reasons. An immediate an actual contemporary example to Dark Souls was Dragons Dogma which did the exact same thing (though I believe the later remaster patched in more conventional save slots).
The multiplayer may have been more or less unique, but its a niche. An extreme niche. Souls-likes are develo[ped by... obviously, fans of souls games. And they completely disregrard this element. Even the Souls games started making it optional with offline modes, and basically turned it into the "difficulty balance" against using co-op more then anything.
Interconncted worlds.... old as dirt. Metroid, Castlevania, Zelda (up until Skyward sword), and all their descendants used this. I have no idea what you mean by "maps are permanent resources". All of the above (and their many imitators and inspiratees) have you criss-cross back and through areas. And usually offer some sequence breaking oppurtunities as well.
I didn't dissect pojtn #4 much, both because its weirdly multipart. But progress based on phisal movement is.... every game with stages and/or checkpoitns ever made. I could apply your description to Super MArio 3, really (also you lose your coins when you die in Mario, for the second bit). Your last bit was of course, the actual "Souls" mechanic, which is well, the main unique point of the series. But a singular mechanic doesn't make a distinct genre (well, beyond the 80s days of "platformer" and such), or we'd have "Nemesis" games, or "limit break" games, or Sanity meter games.
Well, the story note is... again, every RPg/adjacent (ie Zelda) game ever. Souls will happily spoon feed you exposition at designated checkpoints when it needs to. Gwenyvere, the Serpents, etc. It does it a lot less then some other titles would because there is, at the end of the day, a lot less meat on that bone to feed you. Some people prefer the more vague or abstract story, some do not. But it doesn't take any major steps outside the box in its storytelling. Maybe the odd missable wiki-or-you-wont-know-it-exists side-NPC quests, but even thats come up before.
