If this new 8m diameter telescope already provides us with so many new discoveries then I can't wait until the ELT with 39m diameter goes online.

ELT will not discover many new objects, it's built to do deeper followup observations of known targets. On the other hand, Vera Rubin was designed to be a survey telescope, repeatedly imaging the entire night sky to discover new objects. It will not do targeted observations, or at least very few.