Because, other than declaring the rule bad... you only ever argued about the Mountain Dwarf. Nothing else.
Lets make it short:
you (or someone else I responded to) said: dwarves and elves as long lived races now have a lot of proficiencies... which makes sense...
I asked: what about gnomes... they are between dwarves and elves and don´t have extra proficiencies.
Then I said, the mountain dwarf abilities are seemingly well thought out and I explained, why it seems that way. Because one of the two abilities is (nearly) always redundand, and the other is usually useful. With Tasha´s rules, mountain dwarves are too good. Either by having great armor proficiencies for wizards and +2 con, +2 int, or by having +2 to two stat and very versatile proficiencies (although that does not make them too powerful in any way, but it is a lot of free proficiencies).
Even if you don´t agree with it, it is still an argument.
I also would not have brought it up if it was not for the goblin, that has a real redundant ability if they become rogues. And yes, I don´t like it, and it seems a bit counterintuitive to have no compensation.
So I really don´t know, what is your problem. If you like the swapping of proficiencies and think that is balanced, that is ok for me. But you don´t have more foundation for your arguments either than just you liking it instead of hating it.
So please make better use of our time and stop. In the end it is all still balanced enough and not worth arguing about, as in the end it just boils sown to taste if swapping is cool or not.
The only thing I want to ask is: how is +2 str mountain dwarf legacy when every other species only have +2 to 1 score and +1 to another (except for half elves and humans). I honestly can´t see any logical way to come to your conclusion.