Putting aside that Chicago weren’t imitating anyone when they originated this music and all those years ago, the only way to fairly judge the chops of the two bands is between LIVE performances . The studio is often bullshit with a lot of music(excluding classical).
I’ve seen Leonid and Friends live twice. They are far better than many musicians live.
Their talent is huge, their love for America is amazing.
I’ve never seen it but I’ve heard they occasionally sing the National Anthem in stage.
When they tour, they use a few minivans so they can see more of America and stop when they can.
People have always played others’ music - because they admire it and think it’s worthy to be carried on.
In the documentary interview, Leonid made the point that he wanted to copy the studio versions precisely because bands play things differently in every live performance. He wanted to recreate what people had heard and recognized from the recordings. That was the point (Chicago never toured Russia, so all the people there knew WAS the recordings.)