In fact without Bitcoin Core, there can be no Bitcoin. Even if you don't run Bitcoin Core (which is totally possible), you will need to connect to someone else's computer. So you need to trust THEIR opinions and at the same time, you lose privacy.
Bitcoin Core, also provides you with a wallet, as I said.
You are going very extremely serious.
Bitcoin Core is one of Bitcoin wallet softwares and Bitcoin is Bitcoin, bigger than Bitcoin Core.
Bitcoin Core is a most favorite wallet software to run a Bitcoin full node but there are alternatives like Wasabi wallet or Bitcoin Knot wallet.
I agree Bitcoin Core is the best but Bitcoin network will still be fine if Bitcoin Core software won't have any further developments.
How to run a Bitcoin nodeRunning a full node[Guide] How to run a Bitcoin Core full node for under 50 bucks