This seemed interesting and I'm glad they posted their "Non goals". For me, and I would assume many others, plugins (which apparently is part of the 20% they don't plan to support) is one of the most critical features to any good text editor. This is one area where I think they may want to reconsider.
"Plugins" can mean many things, ranging from dynamically loading parts of the app to having an embedded scripting language.
I'm fine with a text editor without plugins as long as the editor can neatly interface with external applications. I used to use some Vim plugins but I found them to be more trouble than they're worth. Now I have vanilla Vim with only some syntax highlighting additions.
Rather than embedding my workflows into the editor, I'd like to embed the editor in my workflows. I don't want to run terminal apps from inside the editor, but I do want to run external apps and get the results in the editor. E.g. Vim has :make and :grep that work with the quickfix list, but this can also be done by invoking make or grep in the shell and piping the output to vim (+ some command line options to read the quickfix from stdin).
For my use, the feature that Vis needs the most is the client-server model, so I can use tmux to manage windows and open editor windows in any terminal session. That, coupled with some helpers to run external apps should do more than 80% of what I'd use editor plugins for.
