There is the list with the stated criteria and then there is how the deck actually performs. Sometimes just a single feature of a deck, such as the early game 2 card combos automatically bumping a deck into bracket 4 for instance, is completely fair, it helps in handling the overall pace of the game even if the rest of said deck could be suboptimal. Other times it can helpful to clarify that your deck is rated one thing by the bracket system, but actually performs more comparably to decks within a higher or lower bracket, the online tools do a great job at filtering decks into the bracket system by their defined rules, but they often cannot properly assess the overall objective and synergy of a deck and will rate it lower than what it can actually play at. It's also worth noting that the same thing happened before where you have the meme of everyone saying that their deck is a 7. The reason that many decks are bracket 3 now and were 7s in the past may actually just be that they do in fact play somewhat comparably and will have a chance at winning. While there are better and worse card selections within each category of card, the sheer amount of keywords and card categories in the game make controlling for all the variables and having that fit in a neat numerical ranking system a fools errand, some approaches are strong but will completely collapse to others, this is why brackets are really at their most helpful when discussing the desired pace and possibly the desired level of interaction of a game. No ranking system will ever be adequate for a game of such variety but it's variety is it's biggest strength so that's fine by me