You are not wrong. Legend of Zelda is categorized as an adventure game. Or sometimes, action-adventure to emphasize the sword-swinging aspect.
This is the kind of thing that people will argue about, but to me, a role-playing video game is characterized by a controlling party (usually) of characters with stats that can change based on the player's actions and/or progress, and turn-based combat.
I think everyone will have a different definition. In my opinion the "Role Playing" element is the ability for the game player to make deliberate choices which alter the character progression.
It can seem somewhat arbitrary. But to me a game like Diablo, Cyberpunk or Deus Ex where you are given a choice (to allocate skill points or similar) which changes the performance/abilities of the character makes its "roleplaying".
On the other hand something like Zelda or Metal Gear Solid the game play tended to change more based around obtaining certain items or reaching a certain stage of game rather than any decision based character progression
Something like Bioshock blurs the line as you make choices about which skills to obtain which alters the gameplay.
I think the defining characteristic is that you can play in different roles within the same game world. Flight simulator is not an rpg, you're always a pilot. Likewise, the content react to your character. Diablo 4 doesn't have any dialogue or level related to character choices, it's an action game with a skill tree.
Yeah, there are bound to be a few oddities, albeit in this case I think technical and market challenges are more a factor than design decisions, coupled with a bit of "this game doesn't really fit as anything else"
Anyway when I wrote different roles I didn't necessarily meant "trough multiple characters"
"playing different roles" is kind of nebulous, though - and especially historically, it doesn't really mesh with what has been considered an RPG.
Depending on your strictness of definition, quite a bit more than "a few oddities" among the RPG classics would not fit this definition, on the other end it would encompass a ton of non-linear P&C/VN/Interactive fiction in general.
I know that the moniker has it's issues when taking it literally, but doing so too strictly makes the term almost meaningless when discussing genres. (..."even more meaningless", some may argue. ;) )
I'm sure I'm not the only one that in Morrowind onwards (heck, Starfield too), I always drag various followers along for the ride to avoid playing solo. In Oblivion it was weeks before I even started the main quest because I wanted to keep Sean Bean around.
I agree this isn't a key definitional point in itself, although I think it contributes to immersion and embodiment within an RPG to have relationships with friendly characters. And I think those are two key points to making a successful RPG: immersion means I believe I am in this world, embodiment means I believe I am this character. They're not discrete things, and there are many ways to serve and balance those goals. Some people's threshold (mine, if I'm honest) is quite high for when a game qualifies to become an RPG, but it seems quite subjective and it's definitely a continuum.
As a MUD enthusiast I think there's a pretty big gap between games that use an interesting story and meaningful choices vs. a game that is literally just role-playing. I think the labels "Choices matter" and "Character progression" are good for capturing the newer versions of roleplaying games while leaving the noun roleplaying for actual RP. That said RP can and is done in a variety of multiplayer engines, I've seen it in Warcraft 3, Neverwinter Nights, WoW, Minecraft and a bunch of other games - but in those cases it's essentially just folks ignoring the actual game mechanics to just use it as a roleplaying platform.
I often draw the line between adventure/action-rpg (Zelda, Diablo, etc.) with traditional RPG based on the reliance of in-game character skills vs player skills.
In a traditional RPG, a character with sufficient stats are bound to succeed more often, whereas in an action game it really depends on the skill of the player.
Baldur's Gate(1), as I recall, does have turns, it is just structured by default that there is no pause at the start of each character's turn. I'm fairly sure there was an option to do so because I remember setting it on.
It also had a strict round order, each character only took an action then passed to the next, with no two characters moving at the same time.
BG1 and 2, as well as several other Bioware games such as KotOR, have rounds as you described but all characters in combat take their actions concurrently within the round. It's not like BG3/D:OS etc where only 1 character's actions are taken at a time.
This is the kind of thing that people will argue about, but to me, a role-playing video game is characterized by a controlling party (usually) of characters with stats that can change based on the player's actions and/or progress, and turn-based combat.