Originally Posted by Isaac Springsong
To be clear, this is not for stating changes to the base rules of 5e or even decrying some of these elements. This is to create a master list of all the elements of the game that make it ‘feel’ like a DoS game, rather than a Baldur’s Gate/D&D game, given that it is such a popular forum topic. I also acknowledge that I have shamelessly stolen many of these items from other posters, I cannot thank you all enough. I will keep this list updated if people wish to add to/remove from it:

1. Choice of color palette
2. Origin characters vs NPC companions
3. All Origin characters discovered nearly immediately in the game rather than organically throughout the entire story.
4. World full of meaningless items
5. World full of meaningless containers/locked chest with very little of value in them
6. Battles based in the environment and not in Character Class
7. Height (King of the Hill gameplay)
8. Backstab (only lacking the ground indicator from DoS)
9. Removing Class identity by making each character a Swiss Army knife, able to do everything (converting many Actions into Bonus Actions that normally only a Rogue would have, all classes can use scrolls, all classes have massive mobility in combat due to Jump, etc.)
10. Exactly the same starting pattern. Start as a prisoner on the vessel (boat/nautiloid) of our mentally flogging enemies (Magisters/Mindflayer). Vessel is attacked and we must take advantage of this to escape. Only everything does not go as planned and we fall off (void/water) and we are saved from dying by a mysterious force. Then we arrive on a beach and we wake up. Proceed to small settlement nearby.
11. Barrelmancy
12. Surfaces *everywhere*
13. Surfaces having overpowered effects beyond just damage
14. Food everywhere that is better healing than everything else
15. Encounter design that assumes you are fully rested for each fight.
16. Every fight involves flashy gimmicks and enemies using a host of special items (elemental arrows, grenades, healing potions)
17. No normal enemies
18. Reused DoS items that don’t exist in D&D 5e (Trap Kit)
19. Succeeding on a thieving check but the target magically knows you stole from them a few seconds later.
20. Enemies have insanely high HP values, needlessly lengthening combat
21. Chaining party members and movement system
22. Shared inventory space
23. Inventory management and UI
24. Swap any gear on and off in combat
25. Screen shake on ability selection, regardless of activation
26. Overly flashy effects for mundane actions (Jump, etc)
27. Stealth sight cones
28. Swap spells nearly at-will
29. Limited to 1 summon per character
30. Being knocked prone ends your turn
31. Turn Based vs Real Time with Pause
32. Overpowering low level characters via magic items (Doubling Magic Missiles damage)
33. Closeup character models for Portraits
34. Teleportation fast travel accessible from anywhere
35. Narrator’s voice is Malady from DoS 2
36. Normal attack with duel-wielding weapons attacks with both at the same time
37. Reused ability names and animations (Great Weapon Master is called “All In”)
38. Same highlighting mechanic of climbable surfaces
39. Same blocky item reveal UI that doesn’t actually show the item (pressing Alt)
40. Same revealing a hidden item graphic
41. Terrible pathing that will lead to allies unintentionally walking over surfaces and traps
42. Merchant UI
43. Giving free items to the merchant increases your ‘likeable’ score for that merchant, resulting in lower prices
44. Stealing from someone with one character while you are talking to them with another character
45. Giant contiguous maps rather than small and more discrete maps
46. 4 party limit
47. Same map and minimap UI (showing interactable ground, map markers)
48. Hotbar UI
49. Resurrection mechanics, animation (being able to magically teleport someone when resurrecting them)
50. Needing to double click to cast ‘self’ range spells
51. Inability to target party members for spells/abilities via their portrait
52. No non-combat exp or reward for avoiding combat
53. Only able to customize 1 character at the beginning
54. Excessively long ‘AI thinking’ delays in combat
55. Lockpicking progress bar
56. Most books and item descriptions extremely short
57. No need to identify magic items
58. Showing the percentage to-hit
59. Being able to right click on an enemy an ‘examine’ them to learn all of their stats
60. Moving cursor around a target can change whether you hit the target or the ranged attack is intercepted.
61. Companions completely block movement
62. Same party management UI in multiplayer
63. No day/night cycle, it’s always the same time of day in the location
64. Cannot adjust starting gear
65. Overabundance of magic items that remove the need to pick certain spells or abilities (Amulets for Speak with Dead, Misty Step, staff with Create Water, etc.)
66. No Fog of War
67. Ability to keep one or more party members out of combat via Stealth
68. No tracking of normal arrows
69. Wallhack scouting via camera manipulation
70. Aimbotting AI (automatically knowing which party member has the ‘least’ in a defensive stat and focusing solely on them)
71. No random encounters
72. Infinitely summonable Zombie companion

+1 for around 90%, great list overall