Does WordPress require it’s developers to manually save, sanitize, validate all the meta boxes?
Yes.
Are there no pre-built options for simple data such as text, textarea and similar?
Not in core, no.
There are plugins like Advanced Custom Fields or CMB2, among others, that simplify this process though. A Fields API has been proposed, but has taken a backseat to Gutenberg.
Really my question maybe boils down to are registering custom post types and meta boxes and manually handling the said above the correct path while developing a plugin for registering different events that would, for example, include inputs for dates, street addresses and such.
Probably yes, but you can do just about anything in WordPress if you want, so it’s not the only option. You could use custom tables, or integrate with a 3rd party or off-site API or almost anything you can think of. How to choose a specific solution to such a broad problem is well beyond the scope of this forum though.