Actually age doesn't matter when you want to buy BTC or ETH, but some exchange rules require users to confirm their identity and of course those who have identities must be over 18 years old. If you still don't have an official government identity, you can rely on the identity of your parents yourself as that would be the best way out.
Or buy BTC and ETH on the p2p market without the need for KYC or on a Decentralized Exchange like Binance DEX which can be used for free to buy and sell lots of altcoins.
I was impressed when you came and understood cryptocurrency at the age of 16. Even at that age, I still didn't understand cryptocurrency.
Myself too thought of the same. It is a good thing OP has known much about bitcoin before 18. Interesting thing, even the tech people weren't aware of bitcoin and cryptocurrencies. At the age of 16 buying bitcoin is possible, but for the same you require a banking account. Almost every bank gives access to create their own minor bank account under their parents. One such account can be created and used for the purpose of buying bitcoin.