SSMS is really, really useful. I cannot imagine an emacs approach would equal it, and if I have to have it around for OTHER tasks, using it for writing SQL is much, much easier than using something else.
The thing about Emacs is that it’s rarely the best tool for the job, including when that job is text editing. Where it shines is the ability to integrate and automate entire workflows. There are some real advantages to having your email, IDE, notes, terminals, and whatever else all integrated and seamlessly working together, even if it’s not the very best at each of those things.
As for the "everything emacs" thing, I'll say this: there is near total overlap between the set of people who do this and the set of people for whom tinkering with emacs is a rewarding hobby. If you just want to get work done, it's rarely the most effective path.
emacs for me is a means to an end: OrgMode. Absent org, I'd never have started using it. Once something else comes along that works as well as org and has a better mobile story, I might move on (Obsidian is interesting...).
I am, generally speaking, not a fan of monolithic solutions because it leads to sunk-cost-fallacy thinking and difficulty in migrating to new tools that might serve a purpose better.
I had a rather nice SQL workflow in Emacs using an inferior SBCL with SLIME and cl-sql. At the time org-babel either didn’t exist or I didn’t know about it, and it was a really nice pseudo-literate environment to explore data.