I don't think there's anything I can say that hasn't already been said effectively, and I agree with OP.
I think it can be added that 19 pvp takes more of a certain type of skills to be effective, core skills which when mastered can make a player great at any bracket. Fundamental skills, if you will.
- We are limited by the lack of movement that players have available from 20 to 85 with mounts, so our positional awareness needs to be on point if we intend on being where we need to be to effectively help our team. Situational awareness is one of the most important skills to have in any bracket of pvp.
- We don't have the luxury of mashing 10+ abilities and getting a RNG kill like 85s often do, we have a limited set of abilities and the judgement call on when to use those abilities to maximize effectiveness is paramount to our success. Prioritizing when and where to use our very few abilities is another of the most important skills to have in any pvp bracket. We master fundamentals at 19, which translates into success in other brackets.
You're right, people always say things like "LOL 3 BUTTON BRACKET IS BAD AND EZ MODE SCRUBS LOL", but think of it like this - try to imagine building a house with every power tool and amenity available to you, and then try to imagine building that same house with only a hammer, nails, screwdriver and screws. It's going to take a lot more skill to build that house with a lot less available to you, and when you build the next house with all of the other tools available, you're going to be a lot better at building houses by that point.
Fundamental skills and abilities tinks, mastering those is what makes us different and more effective than your average 85 player that just learned to pvp.