One of the biggest mistakes of cryptocurrency was calling it cryptocurrency.

Distributed Ledgers have multitudes of use cases. One of them is as a currency, but you don't need the base layer to be a currency. ETH doesn't need to be spent as much as its needed to act as a quantitative measure of ownership and buy in. You can build a currency on the second layer, which has been done.

Can you elaborate on this a bit more? Doesn’t ETH on some level have to change hands for work to get done?

People are never going to be using ETH as a currency. They would use stablecoins like DAI pegged to USD or a basket of assets.

A high price of ETH as an asset creates a higher security level for Ethereum the blockchain. The ecosystem of projects, apps, protocols, organizations, etc on Ethereum is healthier when the blockchain is guaranteed secure and stable for everyone to use.

It's not about making it deflationary, that's just a side effect of needing to burn the fees for the fee stabilization mechanism. I forget the details exactly, but if you don't burn them then miners can still do funny business.

[removed incorrect post, thanks for the correction]

I think you're confusing deflationary with depreciation.

Deflationary currency means over time, there's less of it, so if the demand stays stable, you'd expect the price to go up.