It still feels weird knowing Big Bird of all characters, who was quite prominent during my childhood days watching of the show, isn't used as much anymore. Sign of the times I guess? Sucks though.
I still stick by what I said however. Even if Carroll isn't physically able to do Big Bird, there's still Matt. So no excuse for his limited appearances. Joey can't write for him? There's other writers. Only legitamate excuse is -and I'm going way out on a limb here when I say this - is if Big Bird doesn't test well with kids like he used to. And I doubt that's the case.
And also, even if they feel he is too up in age to still operate the bird, then they could always write some good Oscar scripts. He worked well in his Word on the Street bits, why not use Oscar for those. Heck, even Big Bird if it means he'll get on screen more.
That's one issue with the block format. As countless others have pointed out, the different segments take up so much time, mainstays such as Bird, Oscar, Count, etc. struggle to find a place within the show. It's highly unfortunate for Big Bird and Oscar, since they were solely created for the street scenes! Which now are basically dominated by Elmo, Abby, Rosita, Telly, and Baby Bear.