The "ich-laut" does not exist in english. It's not like just saying "ish."
Example: https://youtu.be/oSIPAMoCzhA?t=195
Example: https://youtu.be/oSIPAMoCzhA?t=195
I recommend you read up on English phonology, as a video for German learners really isn't a good source.
Yes, one does not NEED to have the mouth open wide to express the "voiceless palatal fricative" but if you do not do it with a "slight smile" as described in that video it will not sound right.
I truly hope you know something about German pronunciation, otherwise I don't know what would compel you to even comment on the thread.