Somebody posted in this thread a while back that they wonder what Frank would have to say about all of this, after the Henson family had pointed out that he apparently was never impressed with Steve's Kermit either.
My thinking is perhaps Frank took it a little too personally like Cheryl apparently has? I mean, there's that urban legend that Frank was overheard swearing he would never perform Bert alongside anybody else's Ernie but Jim's . . . could the same be said for Jim's Kermit? I could see that as a possibility: after all, Frank was perhaps Jim's closest associate, and I suppose I could see that Steve coming in and taking Jim's place probably did not sit well with him for personal reasons. It's kind of like BEWITCHED: for all the crap Endora put Darrin through, Agnes Moorehead and Dick York were apparently very close off-camera, and because of that, she was not happy in the least that Dick Sargent came in and took his place . . . I'm fairly certain Frank probably felt the same way after Jim died.
At the same time, we all know Frank's reputation for being an arrogant a-hole at times - I was surprised to see him at all in I AM BIG BIRD, but he admitted he felt sorry for Caroll in the beginning because Caroll was so awe-struck by Jim that it affected his performances, and he apparently didn't fit in too well with seasoned Muppet Performers like Jim and Frank in the beginning. At the same time, he also spoke about the camaradery on the set in the old days and how much he missed that.
Still, I'm guessing that Frank's alleged not being impressed with Steve's Kermit is pretty much because Frank didn't want to work alongside anybody other than Jim when it came to Kermit and Fozzie or Piggy, or Ernie and Bert.