Although the WordPress gallery block that comes as part of WordPress, is good, it could be a little better. It could for example include a lightbox, and some different ways of laying out the thumbnail images. If you want extra stuff like that you will have to use a plugin. But there are so many.
I found a simple free one that does a good job and integrates with the WordPress gallery.
Once installed, this plugin provides four options for thumbnail layout and function.
The video shows you how this turns out.