They aren't infeasible; a real lisp could target Python. However, just bolting on lisp syntax to python ends up in an uncanny valley of "not python" and also "not lisp."

I would actually recommend watching the entire youtube video I posted earlier (Clojure for Lisp programmers). Rich talks about a lot of the design decisions that went into Clojure. Some decisions I agree with, some I don't, but there was thought into creating a unified whole and he was clearly aware of work that had gone before, even when he chose to do things differently.

Note also that Clojure was his third attempt at doing a lisp/java interop, so there was a lot of previous experience backing many of those decisions.

Lastly, it's really easy to make a bad lisp-frontend for a language and a massive amount of work to make a good one. This is well known by anyone who has been in the lisp community for a while (if for no other reason than they themselves have made a bad one) so for better or worse, such frontends tend to be ignored.