Magento2 language/locale not working

So I installed Magento 2.4 via docker/composer on my development machine.
I am trying to use the German (Germany) language for my store front view. I tried with just the default setup, I also tried using a i18n language pack (https://github.com/mageplaza/magento-2-german-language-pack) and i10n language pack (composer require community-engineering/language-de_de). I am unclear if I need any or all of these packs?

After doing all that and setting the Locale in the view settings, setup:upgrade and cache clear/flush, reindex, restart, switching to this view in the frontend changes almost nothing to German language. It changes a few words like "or" and "required", but that’s almost it. I tried using Magento Luma default theme and also Solwin FreeGo (which I’d like to use).

For example from creating a new account, almost everything is in English:

Create New Customer Account
Personal Information
First Name
Last Name
* Pflichtfelder

Is localization really so bad for Magento or am I missing something here?