WordPress is very slow (objectively) and much more complex to get started with (subjectively). Also the security model of WP isn't great (PHP/MySQL/etc).
Much more complex to get started with compared to what Ghost? Really? Almost all shared hosting services offer a single click install of WordPress, I don't think ghost is anywhere as simple as that to install(for a non tech savvy user)
WordPress has improved a lot in the past few years in terms of security, "worpdress is insecure" is an old meme. Sure if you just go on installing any plugin under the sun, there can be a risk. But the stock installation of WordPress with just a handful of reputable plugins should be good. Much of the slowness comes from the oodles of plugins that people install.
For speed, there are many great and free caching plugins available for WordPress which can considerably speed up your site.
I meant less complexity with the setup and more complexity in just "starting to write a blog". I have used both and I found the experience with Ghost much nicer.
WP will never be faster (and will use more resources) than a JAMStack website.
WP will never be more secure than a JAMStack website. It is literally impossible to deface my static Ghost blog without compromising my upstream provider. This is obviously not the case with any WP site.
WP definitely has its uses. I don't think a personal blog is a good one.
