Sure. It's also absolutely invisible to users; you can have a fulfulling and engaged social life on a server that doesn't implement nodeinfo, and never know that it's missing.
All that said, I think being part of "the Fediverse" means a lot of different things to different people. For some, "the fedi" is more about a particular set of shared values, and even the most fastidious implementations of specifications won't be enough to be part of the Fediverse.
