I don't like that I can't get the best items without some investment

[Rare]

Yes I did spend money.

And that's the benefit of spending money.
You had to farm, but I didn't have to.
And I gift my wife the best set to play with. So she didn't have waste time to farm, but have just fun.
Some people enjoy farming, we don't.
I would rather play pvp or finish quests and achievements.

It's just because what people think better is different.

No I'm not saying anything negative about buying your gear. To each their own. But you mentioned in your post

What really bothers me is not that we have to spend plats to buy pets and open chest,
(I think spend money on a game is the best way to show respect to developers.) but that what I bought with plats becomes a crap.

That's kind of part of the game. You spent the plat to get your gear fast without having to farm. Which is fine. But it does have a shelf life. (Let me qualify this by saying I don't think the same is true with these Arcane/Mythic items. These things are so enormously expensive I think they SHOULD have a much longer shelf life).