Quick idea: the liquid seems to be less transparen because of some micro floating particles (the real one not from blender) so maybe adding some “substance” to the liquid… some fog for example…
That’s literally almost what i did but with a principled, i am so angry at myself right now for not hooking up the individual glossy and transparent shaders and giving it a try
Principled is ok for simplifying workflows - but I always revert to individual shaders. I just prefer building my shaders from the ground up, allows a greater level of control and understanding IMO.