Conversely, even if the official project implemented an onion blacklist, a fork would quickly appear to remove it. And node operators would likely prefer that one.
Anyone with any sense understands that introducing a node blacklist creates the capability to expand the use of that blacklist in the interest of political and/or military censorship. The Tor project, Tor devs, and node operators are adamantly opposed to any such censorship capabilities. Therefore it will not happen, period.