There is an inherent value in syncretism that I think is often overlooked. Syncretism doesnt mean that your worship of a god becomes one huge muticultural gobbity gook, but rather it is very effective way to develope a multi faceted understanding of your deity. That is to say, my understanding of my god is vastly expanded through syncretism. But this does not mean that my deity is necessary going to be subplanted with another.
For instance, Apollon as Rasheff brings a certain insight, as does Apollon as Horus ( though really I think the combined Horus and Seth to be more point on, so does my interpretation of Apollon as Shiva. But he is still Apollon. I may find myself happy to worship with followers of his other manifestations, but these other forms are not the ones that I live with so to speak. But it does have the benefit of added clarity. I never truly had a good handle on the benevolence if a destructive god until I got to know him as Shiva. That is but one example.
Syncretism doesnt change your relationship with your gods, and may even never directly impact your worship, but it does its magic on other levels. It does not need to be shunned.