The concept of cryptocurrencies were to remove trust but tools like metamask require you to trust them with your front end.
closed as primarily opinion-based by Richard Horrocks, Majd TL, alberto, Achala Dissanayake, Sanjay S B Aug 23 at 4:25
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I'd say no. Metamask is exactly the kind of user interface that can be built by anyone. The idea is that you don't have to trust the blockchain because that's trustless (or exactly because of that you should trust it, depending on your point of view) so anyone can access it safely with whatever means.
However to access the blockchain one needs certain tools. These tools are typically centralized but they can be replicated by anyone. They are only ways to facilitate the usage of blockchain.
So the backend (blockchain) remains the same for everyone and is accessible by anyone but for convenience there are various centralized products built on top of it. You are free to build your own and utilize exactly the same backend.
They could possibly be one.
Although in their current state they don't steal any data. (at least from my knowledge)