I guess we will have to see his stats at his new club. He was performing at a high level before Poch but nothing like what he did after Poch changed the system etc and honed . Poch improves players that have natural ability and work ethic, it's well known that's one of his best qualities. Some players like Nkoudou and Janssen don't have the required ability to play at elite level so it's unfair to suggest Poch is to blame for not making them world beaters.This one doesn't pass the smell test. Eriksen was here the season before Poch came, and he played at a high level. Poch's pressing system has played to Eriksen's strengths, but he's a very good player with or without Poch.
I am also not at all sure that whoever we replace Eriksen with will have similar stats. Poch is an excellent manager but he can't transform every player who comes in into a world beater. We've still got the Janssens and Nkoudous, etc. For any professional player in the highest leagues, the number one driver in their development is themselves, not their coach.
I agree the number one thing for a player's development is themselves but an elite coach can make them something else. Coaches like Mourinho do not make players better, he generally wants finished articles to implement his style and to the contrary Poch moulds them.