Both of those theories are actually pretty significant: there are a number of "purists" out there, who outright refuse to at least look into any post-Jim Muppet fare, which is sad, because Jim wanted the Muppets to continue after he left us - that's actually why it was Disney he chose to sell them to, as they kept Mickey, Minnie, Donald, Goofy, Pluto, et al alive long after Walt's passing. Granted, post-Jim Muppet fare isn't the same as what Jim did with the Muppets when he was alive, but not only is that to be expected, but also, consider this: even when he was alive, Jim was always looking into different areas to branch out into and develop projects for . . . for all we know, Jim could have, eventually, sort have abandoned the Muppets altogether, and began dabbling in other areas. I could easily see him diving into the world of 360 VR filmmaking right about now.
As for the CGI thing, yes, that's unfortunate, and it's also affecting traditional, hand-drawn animation as well.