This is where the difference between theory and reality start to become an issue.
Yes, in theory the full node contains the full blockchain. Yes, it's all you need to verify that any transaction happened. Yes it's tamper proof.
But in reality, it can't show you the full side-effects of every transaction. In reality there are occasionally things things that require archival data. In reality, it's always easier to go to a centralised block explorer, or pay one of the few centralised API services (And I know this from experience, I've synced a full archival node back in 2019, and build a product that required querying it. It was such a pain that these days I'd highly recommend not doing that and just paying for API access)
In reality, the fact that you occationally need to go to etherscan to get the data you need, results in you just going to etherscan anyway, even for the simpler queries when you have a perfectly fine full node sitting there (again, personal experience). Hell, etherscan actually provides more data than an archival node, where else are you going to find the source code for contracts?
In reality... Most people don't even run light nodes. They certainly don't run full nodes. They just use etherscan, or whatever API their 3rd party wallet uses.
That's why in reality, access to ethereum is partially centralised around API providers. Yes, in theory anyone can go around them, set up their own node or create a competing API service at any time. But that's not what happens in reality, and when it comes to the topic of centralisation vs decentralisation, I'd argue that reality is far more important than theory.
Yes, in theory the full node contains the full blockchain. Yes, it's all you need to verify that any transaction happened. Yes it's tamper proof.
But in reality, it can't show you the full side-effects of every transaction. In reality there are occasionally things things that require archival data. In reality, it's always easier to go to a centralised block explorer, or pay one of the few centralised API services (And I know this from experience, I've synced a full archival node back in 2019, and build a product that required querying it. It was such a pain that these days I'd highly recommend not doing that and just paying for API access)
In reality, the fact that you occationally need to go to etherscan to get the data you need, results in you just going to etherscan anyway, even for the simpler queries when you have a perfectly fine full node sitting there (again, personal experience). Hell, etherscan actually provides more data than an archival node, where else are you going to find the source code for contracts?
In reality... Most people don't even run light nodes. They certainly don't run full nodes. They just use etherscan, or whatever API their 3rd party wallet uses.
That's why in reality, access to ethereum is partially centralised around API providers. Yes, in theory anyone can go around them, set up their own node or create a competing API service at any time. But that's not what happens in reality, and when it comes to the topic of centralisation vs decentralisation, I'd argue that reality is far more important than theory.