Hey all - I really love emacs as a text editor and environment, but I’m wondering…
Does there exist something that is…
I’d love to hear if there’s anything you’ve found beyond the Mariana Trench!
Will
I guess not for the same category but you could try to define the category you’re looking for exactly and things could change.
More customizable than Emacs? What are you having difficulty customizing?
More mature community and giants to stand on (like packages)… Did you look at the result of running M-x list-packages? Is there a package missing you aren’t finding? Did you try looking at the MELPA repo (MELPA) - N.B. If you have configured Emacs to do so, M-x list-packages will show packages from GNU, Non-GNU and MELPA… there are thousands of packages.
Stronger expected lifespan - Emacs has been around for almost 50 years, there is still ongoing development and new features added every release.
Realistic enough to actually commit to - that’s subjective, I’ve committed to Emacs (I have tried other editors, and I kept coming back to Emacs - it just works well for me).
I guess I’m not sure how to address your question. I pose the questions and suggestions above with the hope they will be helpful to you or maybe help you frame the question “better” (for some definition of “better” 
)
Lifespan: Emacs is one of the longest lived software which has a incredibly large footprint.
More customizable: You have all the source of Emacs to do that. It is free software - you have 4 freedom.