)Since there was a time when the mitzva was unable to be done, that creates a mesorah to not do this mitzva.
I never said that. It could just be that theres a reluctance to change on anything, and that could well be the sole basis upon which a Mesorah can suppress techeiles. Nothing to do with a mitzva-specific mesorah not to do it. It could also be that the reluctance increases as time goes on.
As far as “who these mysterious daas torah gedolim are”, go ask a R”Y whose yeshiva that does not wear techeiles because of Mesora.