The crema is the oil of the bean. visble by using presssure and hot water. It holds all the good of espresso. take the cup away from the pour before you see the shaky light (pasty watery fluid)
aim to find the blend and method to pull the shot that suits your taste without sugar. It can be done. Filter your water.
I have had the priveledge and on occassion a bloody nightmare over some years to use and abuse, pull apart and resurect some great machines. Literally hundreds. Whilst I can not grade the MOST important ingredient to making a great cup of coffee - beans, machines, barista, environment or vessel?
I can suggest the most noticeable differences have been due to a good grinder and *a great barista.
I have seen ordinary beans put through throw away machines yet ground in a good clean sharp bladed grinder, tamped and extracted by a caring barista to produce a pretty good cup