The Blaschkas were absolutely some of the most talented glassworkers ever, and it's true that many, many skills and formulas in glass have been lost over time (most notably during WWII, when many glass factories were shut down or repurposed) but two things worth noting are that the Blaschka's work is not glass alone, particularly the elder Blatchka, but also incorporates paint and wire in order to create the most realistic replicas possible. The painting was done almost exclusively by the younger Blatchka, who, after his father's death, incorporated more and more colored glass into his work, which did not require painting.
The second thing worth noting is that there are still glassworkers specializing in botanical, insect, and crustacean replicas, and many of them are very skilled.
http://www.paulstankard.com/works.htm
http://www.lindemannglass.com/gallery/galleryfrset.htm
http://www.wesleyfleming.com/gallery/index.htm
Michael Lindemann's dragonflies, which I don't have a link to, are spectacular.
There are also more general sculptural glass masters like Lucio:
http://www.luciobubacco.com/public/index.asp
What is really missing from today's glass artistry are the sponsorships, grants, large commissions, and patronages that would allow a glassworker to spend the time it would require to create such an impressive library of replicas. Even Lucio must worry about making money and paying his bills, and that means production work, and teaching classes.