Wicca, like all other religions, is syncretic in its origins. Others have continued this process ever since. If the Craft had remained as Gardner first envisioned it, it would never have survived and grown to become the viable religious movement it is today. If it does not continue to grow and change, it will not remain viable. The Catholic church is an object lesson in what can happen to even a large, well-established religion if it refuses to grow and to change.
Eclecticism means different things to different people.
Unfortunately, many people in the Craft see eclecticism differently. The discipline of formal training is valuable. With training, a Witch starts by receiving as much as can be transmitted of the skills and experience of one's teacher, and one's teacher's teachers. It's not as easy as skipping the hard work of formal training, but neither is it as safe and comfortable as subscribing to a single name-brand tradition. There's a lot to be said for the comforts of tribalism, of having a home and family to identify with, within the broad sprawling structure of the Craft.