lets get the obvious out of the way. you cant activate it and it has no destination.
where it would lead to
if it leads to some place like the end (boss fight with other features) then the boss would clearly be way too overpowered because the warden is very strong and the boss for sculk would have to be stronger. the game wouldnt be as fun if there was a boss with 1k hp and can 1 shot you in fully enchanted netherite (concept).
if it leads to some place like the nether then that seems a bit more reasonable however what would be in the new dimension? unlike ruined portals the ancient city seems to have all sculk features no need for a whole other dimension.
if it lead to other ancient citys that would be extremely overpowered. the citys have really good loot especially enchanted golden apples. they already messed up by making totems farmable i dont think they should make enchanted golden apples way easier to get.
how would you light it
flint and steel is way too unnatural for sculk.
ender eyes are.. ender.
this leads to most likely echo shards, the most reasonable about the portal being true.
also we need to let sculk die please let it die already i dont want caves and cliffs 4