This is one way to look at it, but ignores the fact that most users use third party community plugins.

Obsidian has a truly terrible security model for plugins. As I realized while building my own, Obsidian plugins have full, unrestricted access to all files in the vault.

Obsidian could've instead opted to be more 'batteries-included', at the cost of more development effort, but instead leaves this to the community, which in turn increases the attack surface significantly.

Or it could have a browser extension like manifest that declares all permissions used by the plugin, where attempting to access a permission that's not granted gets blocked.

Both of these approaches would've led to more real security to end users than "we have few third party dependencies".