Are all Blockchain array implementations incorrect

Question

I found many Blockchain implementations on the web, but is it true Blockchain that can scale? Here we can see that the blockchain is started as an array

var blockchain = [getGenesisBlock()];

Here we can see the same implementation:

constructor() { this.chain = [this.createGenesis()]; }

This article also recommends it:

constructor(genesisNode) { this.chain = [this.createGenesisBlock()];

However, are any of these implementations ready to scale?

The real problem that I'm thinking about is, how long would it take to read the last element of the array and would this be scalable? In the blockchain, the 'Block' structure always needs to read the hash of the last block, therefore I assume that as it scales it takes longer and longer to do it.

What would Bitcoin and Ethereum do if their Blockchain array of Blocks doesn't have any more space to store blocks? Would the Blockchain just end there?