It uses "Bitcoin" to refer to the protocol, not the BTC network. People fought about the name "Bitcoin" for ages and everybody has their own opinion about this topic. The network that you refer to as Bitcoin has forked several times as well and least resembles the original protocol and idea when compared to BCH or BSV. OTOH the market values it the highest.
> Someone created a block chain and network for mass data storage.
I don't like the phrase of storing data on the chain. The blockchain is not a storage medium but a network that incentivised connectivity and data propagation.
Except for an early hard fork due to a transaction verification bug that allowed for infinite Bitcoins to be created, the main Bitcoin chain, as implemented by the Bitcoin Core client, has never forked, to my knowledge. It also seems disingenuous to claim that it doesn't resemble the original protocol, when the block size cap that the forks adjust, was put into place by Satoshi himself.
BTC hard forked twice (or thrice if you count the one accidental hard fork) and soft forked a dozens of times. Claiming that BTC is the "main chain" is misleading. The main chain is dead for years; run the original bitcoin client, it won't sync up.
"Removing instant transactions?" Do you mean "the GUI shows 0-conf transactions as pending?" And why does adding Segwit make it "not bitcoin anymore"? Further, the Bitcoin Core devs didn't alter the protocol, the miners and users did by using the voting mechanism to enable Segwit, entirely of their own volition.
> Do you mean "the GUI shows 0-conf transactions as pending?
It's not just GUI but also a miner policy which can break the use of BTC as cash - as it was originally intended.
> And why does adding Segwit make it "not bitcoin anymore"?
It's an ugly addition to the original protocol that among others breaks the definition of a coin as a chain of digital signatures. This might lead to legal issues as some people (including lawyers) pointed out.
> Someone created a block chain and network for mass data storage.
I don't like the phrase of storing data on the chain. The blockchain is not a storage medium but a network that incentivised connectivity and data propagation.