I agree with you that Twitter's feature velocity has been terrible. Although in the last year or so they've definitely been trying more new things, so maybe they've finally fixed the internal barriers to that.

But I'm not getting what you think "Twitter for the masses" should be. The current value prop is something like, "globe-spanning discussion around hot topics". Fewer people care about that than "keep in contact with family and friends" or "look at pretty pictures". I don't see a mom-and-pop version of Twitter in the same way that I don't see a mom-and-pop version of the WSJ or the NYT. The mom-and-pop version of the NYT is perhaps USA Today, but that's not an expanded product, just a different one.