Okay so how did we go from this...
One is an art style trying its best to emulate Ninja Turtles. The other just looks like a cheap kids program on Disney XD. It's like somebody liked all those terrible Turtles reboots and decided to hire the artists from them.
Well, the latest Ninja Turtles aren't looking all that great either.
Quite simply, animation in general has gotten ugly in the past few years as animators have discarded the whole concept of "appeal" for reasons that have never been made clear to me. Even Disney's followed that trend recently in some areas with projects like the Mickey shorts from Paul Rudish and to a lesser extent the latest DuckTales.
I don't know why. Cheap computer animation shortcuts may be a part of it, but other shows like My Little Pony have ridiculous amount of appeal in the same environment.