What's wrong with iFixit? They're ecommerce system is smooth and easy, compared to Samsungs trash website, and Apple self service parts supply nonsense store. And iFixit can provide tools and guides.
As a general note, centralized platforms are never quite good - if all your parts for all your products only exist there, you're at the mercy of their warranty policy, pricing, customer support, all of which can change.
But being specific... they abandoned my country. Even if I were willing to pay exorbitant prices for shipping, without any explanation, they simply stopped shipping here a few years ago. So if companies now only provide parts with iFixit, I'm being left out. They're parts, there's no reason they can't be sold on every e-commerce platform available, iFixit isn't special in that regard.