Depends on what you mean by "viable". Food is a huge part of culture and while those items you listed do provide protein it's, in my opinion, no where near as enjoyable as various types of meat. In fact many of that, to me, is really gross and I've tried multiple versions of all of it.
Naturally to others meat may be gross. There isn't a one size fits all solution here. We've evolved taste for a reason and it's hard to ignore if you don't like the "other solutions".
So I would say I disagree with your statement when you call the other items "viable other solutions" :)