UTXO vs Accounts

[sordum]

One of the projects I've been following has recently published an article about UTXO vs Accounts.
I didn't fully understand it, so I decided to ask here. Maybe I should chew somebody up, why is it so important?
https://ergoplatform.org/en/blog/2020_03_03_building_utxo/

[SteamCoin]

I don't see why UTXO vs Account is such a big deal. Blockchain is immutable anyway, right, in either case. So surely it doesn't really matter what model you use, so long as it's immutable.