What's wrong with most people???
The Original post so clearly mentioned what insignia has changed even showing the old one side by side with the new one! SO WHAT'S ALL THIS NOISE ABOUT THE MAARKHOR???
So if the maarkhor was an unofficial symbol or logo or whatever for ISI before then it can/will stay so even now. Nothing has even changed in that regard!! So what's the issue??
Regarding the insignia everything inter services has typically had one that is tri color, those being red, light blue and navy blue and representing army, air force and navy. Like the ISPR, JCSC etc. Same thing applied to ISI. That golden insignia you see also has three parts and is also used in tri color as describes above.
Just look at the arm patches worn on uniform by chairman JCSC, DG JS, DG ISPR and you will see the tri-color patch. Whereas other army officers (including army chief) will either be wearing the Pak army insignia/logo or respective formation (e.g. corps) insignia/logo etc.
Now look at any old photos you can find of any former DG ISI in uniform you will see they are also wearing a tri-color arm patch. HOWEVER look at some recent photos of DG ISI in uniform and you will see he is wearing the new green arm patch rather than a tri-color one. (I have seen some photos of Faiz Hameed with new arm patch quite recently but can't recall where).
So that's the change that has taken place. ISI officers even in uniform never wore any maarkhor logo on their arms! And therefore if their was any unofficial logo with maarkhor it's still unofficially there and maarkhor lovers can now sleep easy.
It is possible that that the new insignia give ISI an independant formation identity rather than a tri-service thing but that is only conjecture since it remains 'inter services' intelligence. Perhaps some one was just bored of the old design.