I reckon much of everyone in the community underestimates how much centralisation there is in bitcoin's decentralised sphere including development. Similar to what you mentioned, internet service providers are centralised. The same centralized internet providers that give everyone access to Github, also a centralised platform. The creators of the hardware where everything is hosted is a centralisation risk.
However, nothing is perfectly decentralised and about this is bad, I reckon.
Centralised internet providers are not ideal and I'm really hoping to see censorship-resistant, decentralised internet in my lifetime, but it's not like they can effectively ban anyone from accessing the internet - if that happens, you could use a different service, at least for now.
Not sure what exactly you mean by Bitcoin development being centralised, feel free to elaborate. But I remember times when many considered Gavin Andresen as having effective control over the entire network. Fast forward, most new Bitcoiners don't even know who he is.
And I don't subscribe to the "all or nothing" attitude, that if we can't have everything decentralised, we should ditch decentralisation altogether.