FWIW, even at my major academic center, we have fellowship-trained folks I wouldn't let anywhere near my family and big-case generalists without fellowships I would beg to do their cases. Nothing about that extra year of training is magically going to turn a mediocre physician into a great one. Fellowships just unlock doors: you can't do hearts*, neonates, round in the ICU, or open a pain clinic without putting in an extra year** (or in my case, two), so if those practice areas are important to you because you LIKE them, then consider doing one. If not, get on with your life.
However, and I say this in the most loving way possible, as an MS3 this is so far beyond something you should be worrying about. Trust me- there are posts on this site from 2013 with MS3-me asking about congenital cardiac anesthesia superfellowship. Complete waste of energy. I don't even like discussing fellowships with new CA1s: waiting until CA2 year reduces the number of conversations I have to have about ICU fellowship by several orders of magnitude. Extrapolating my own experience, I imagine you are thinking you might like anesthesiology, but are concerned about the future and are trying to make yourself feel better about applying. Dude/dudette: just find something you think you might like- you're going to be doing more of it than you can possibly imagine. Culture, reimbursements, scope of practice, etc etc- it all can and will change, for some specialties in wild and unpredictable ways, some for the better, and some for the worse. But at least if the field interests you you have that fascination with the subject to fall back on when the hospital hires an freshly graduated administrator to sit in clinic and critique your workflow (happened to a surgeon friend of mine a decade out of training- the new hire had actually been a student in a class he teaches).
*Not interested in the debate about doing hearts/TEE without a fellowship. Yes it's possible, but I stand behind the notion that people who love doing hearts should consider an ACTA fellowship
**Again, making generalizations here, but the majority of people doing these things have fellowships, or will have fellowships in the future