To Topgoon,
I'm not completely against it, but it's new mechanic to 5E that will need to be considered across the board (I assume if we are letting resistances stack, it needs to be across the board and not a Ranger exclusive). Do only permanent resistances stack this way? What happens when there's 3 sources? Another side-effect that will be hard to calculate isn't in the damage reduction, but what this helps you avoid when certain spells/abilities that do more than just damage. Very similar to the Poison Resistance vs. Poison Condition situation I outlined above.
1varangian was only talking about giving a saving throw bonus instead of a resistance - since the saving throw bonus would compliment and add to the resistance. They werne't talking about stacking multiple resistances.
My wording might have been a bit confusing, but that's exactly what I was talking about whenever I mention "stacking resistance" - as in normal resistance = 50% damage reduction. Stacked resistance = 50% damage reduction + Saving Throw advantage vs. the associated elemental type. That's what I mean by the Poison Resistance vs. Poison Condition - right now resistances do not help you against any "rider" effect of elemental spells.
Like I said, I'm not completely against it - it's just something that needs to be evaluated more deeply (i.e. to see what it affects overall). Many spells have a save for 1/2, so this means you're effectively giving further "expected" damage reduction in those cases. On the flipside, the extra saving throw means "rider effects" - aka Thunderwave's knockback for example, will also become less effective.
For the other bits:
5e design is more careful than you think about its style for allowing overlaps and double-ups.
-- snipped for length--
I actually talked about the design aspect at the beginning of my post:
Right now, other classes tend to their resistances around level 6, and almost always as secondary boost (i.e. only 1 part of the suite of goods you get). E.g. Draconic Sorcerer gets a elemental damage buff ability + an associated elemental resistance. Giving this earlier to Rangers kind of gives them a nice niche, and is by no means OP since you can easily get that at level 1 via racial traits anyway.
My feeling on this is that while it deviates the current design conventions, I don't see a problem with it and feel like it gives the Ranger something unique, which neither PHB nor even Tasha's update really provides. The fact that elemental resistances is always given as just 1 part of 2 abilities at level 6/7 tells us that WoTC doesn't think it's powerful enough as a sole 6th+ level ability, which I agree with. Which is also why I don't think it's overpowered to be provided at level 1. The fact that this is put into the main class chassis vs. a subclass feature isn't a concern for me either. Some classes draw a lot more power from their subclasses (i.e. Warlock), others draw more from their base chassis (i.e. Paladins).
In regards to the elemental redundancy, just because the redundancy comes from racial + level 6 subclass feature, instead of racial + level 1 base class feature, doesn't change the core problem that having thematically aligned race/class choices leads to a suboptimal mechanical reward.
In fact, having a redundant feature come in at level 6 is WORST than having it at level 1 IMO. It's a much larger investment of levels. As you go up in levels, each class ability you get should be more attractive. Lastly, remember that the BG3 Ranger gives you a choice of abilities, whereas a Celestial Warlock/Aasimar, Draconic Sorcerer/Dragonborn, and Fathomless Warlock/Triton is actually 100% locked in.
Giving flat fire resistance as an entire first level perk is a very clear misstep made by someone who is not well versed in the system and style of design, and doesn't understand properly how things are made to fit together.
I must disagree on this.
"This is how we've always done it" is not a fantastic design philosophy, and is exactly the line of thinking that led to some flawed 5E classes/mechanics not getting the fixes they needed, or just severely delayed - like the Sorcerer (i.e. the extra spells with Clockwork / Aberrant Mind). Very grateful that has changed. Some of the best fixes in 5E comes from uprooting previous designs (i.e. most of the current summon spells), and I think each of these updates need to be evaluated not by how much it matches the previous design language, but it's actual impact in the game.
At the end of the day, WoTC is involved with BG3 as this is IP as well, and if there was a fundamental issue with it, it would've been flagged.