Elden Ring is probably the best game ever made but due to its size and ambition it definitely has area's in which it could improve for a sequel.
1. Enemy Level Balancing: Right now its really hard to control how difficult an area is supposed to be for a player due to grinding or just exploration, as a result alot of area's that are supposed to put up more of the fight can be insanely steam rolled during certain parts of the game. One egregious example that comes to mind is Fortissax, the build up is epic but where he is located in the game just is almost impossible to be at an appropriate lower level to fight him. The type of solution I would go with is to have enemies level up with you to some degree every 5 levels, things like what the expected level for the player should be for that area could influence how this works as well, they could even have Tier brackets they could hit that would cause them to gain new move's or different/more difficult behavior's to deal with depending on what Tier they have entered into (besides just gaining some health and attack). With it being every 5 levels the player will still obviously feel the progression and become stronger but it helps keep in line the intended difficulty for certain areas and even helps keeps player's on their toes upon return trips to older area's due to behavior changes.
2. Summoning Balancing: Another thing that is currently incredibly overpowered (but really cool) are the Enemy summons in Elden Ring. For a sequel I would want them to adhere to your build more as a means of balancing and progression. For Example I would have the Grave Glovewort upgrade now only apply to increasing the Summon's Health and some Attack Power but for the summon to gain better attack behaviors, more enemies summoned for a group or unique properties they would have Scaling Tier with Stat Thresholds that the Player must meet or some condition (like wearing certain clothing/weapon) to get the best results out of a Summon. This makes summon's more interesting since they adhere to your build (not having everyone just pick Mimic Tear) while keeping them all technically usable as long as you can pay the Mana requirement.
3. More Horse Options: I love torrent but I would love to have progression throughout the game involving improving him maybe with upgrades or some sort of saddle or special moves, something, give me a reason to feed Torrent. Honestly I want your moveset to be a little more involved on horseback as well with maybe a few new move's for weapons while on horseback, some builds around it would be dope as well. Also let us remap the click in on and off for torrent.
4. More Wondourous Physic Options: love the wonderous Physick but cant stand you only can use 2 ingredients the whole game, they need to let the player play around with this more and be more open to possibilities. Id love for their to be upgrades that you could get that let you combine more than just 2 together for let you have multiple different physic potions. Personally Id create a system similar to choosing your Red vs Blue Estus, so after finding all the upgrades you would have a few options, you can have up to 3 different physic potions with 6 ingredients to play around with the more ingredients in a physic the less time it lasts (max amount of ingredients in a physic is 4).
5. Make Great Rune's more impactful/interesting, when you use a Rune Arc it should definitely matter and have build ramifications, it was really disappointing that only 2 of them actually did anything and they were pretty basic. Hell even giving you exclusive access to special weapon arts while active or something could be really cool, there's alot that could work.
6. More interesting Crafting Stuff: Give more stuff to Perfume Builds and Pot builds, one of my favorite surprises was finding the Perfume Bottles and realizing how it made those crafting items Ive picked up actually useful even though not necessary.
7. Dont be afraid of giving bosses a Second Health Bar: We have summons and a ton of advantages going in our favor with an open world, its a tragedy that Maliketh or Horah Loux didnt get a second health bar, its late in the game Main bosses typically deserve a second health bar alot of the time, these fights should not be pushover's.
8. Add the cut Bestiary with lore: There are so many cool enemies that you discover in this game, I know originally it was going to have a bestiary and that just seems like such a great idea to learn more about the world and how to approach difficult foes. Id even be fine if you slowly obtained information on them somehow.
9. Add a light Journal for NPC's: It's very hard to naturally hit an NPC's quest fully in this game without a guide and I think its a shame that it's like that because these are some of my favorite NPC's ever almost all are unforgettable except maybe Diallos lol. Im not saying you just spell it out but you have the part of the dialogue you had when you first encountered them that hints the most towards their next location remain in the NPC journal to help guide the player to search for an area similar to what they mentioned.
10. Elden Ring II just add an Easy mode so they stop nerfing these incredible bosses: There has been a bad trend lately with From Software of nerfing bosses for no good reason, AC6 they went way overboard, Im fine with things that clearly feel unintentional like bugs getting patched but the bosses just being difficult is there for a reason in these games and there are plenty of ways to circumvent it, just give them an easy mode so I dont have to see Elden Beast nerfed or Baltius nerfed again please its not worth them being lesser when they were so perfect originally.
11. Dont Ask if I want to Revive Torrent or keep the hit Triangle button when entering combat, the answer is yes or Im busy right now, get that annoying crud out.
12. No more Godefroy's: I understand repeating miniboss's or remix's (poor ulcerated tree spirit lol) but Main Story bosses should be untouched sacred cows, it diminishes how epic they are in every sense when you just randomly find a slightly remixed version of them out in the wild, takes you out of the game.
Anywho that should do it for my big changes improvement wise, Im sure im forgetting some stuff but the biggest ones are here either way I just hope we get ER 2 within 5 years.