I don't believe it's a waste of time (obviously since I'm one of the organizers). But also, the United States and Israel are the only 2 countries that have consistently voted against this measure when it comes up (and it does almost yearly).

This year at the Summit of the Americas hosted by the US in Los Angeles, where countries from all over North and South America met to discuss the future of the continents, many refused to send delegations or sent lower-level delegations than they normally would have. Why? Because the United States decided to exclude Cuba, Venezuela, and Nicaragua. The countries that denied or limited their participation weren't necessarily left-wing and some are unapologetically right-wing. They simply decided to stand up to US bullying.

So no, I don't think it's a waste of time because opinion is turning against the US on this issue, and the US is the primary obstacle to progress on this and only upwards pressure from the people on this will change the course of the United States regarding the blockade.