Well, I'm not 100% sure what you mean when you say "current static site generator tools," I think of things like Webflow and other WYSIWYG generators. And for those, I end up not liking because of some experience at work being handed these sites that are impossible to dig through because of all of the useless functions in the JS bundle and CSS that never get used so they just bloat the site.
As far as Firebase is concerned, I've been in love with it so far. I've been using it as a storage bucket for assets I show on my personal website, as well as a sort of CMS where I update my portfolio there and it's reflected on my website. I am looking at it now for doing a webstore sort of thing so I'd have to get back to you on that.