Maybe the new fixture itself was defective.
When you connect the black and white wires of the fixture the same way as the black and white wires of the old fixture, the new fixture should work for better or worse the same way.
Or maybe you took apart more wire nuts than necessary and didn't put it back together properly.
The ground wire (bare wire) must not be used as "an extra conductor". All ground wires are tied together wherever they come together with a pigtail or long end attached to the outlet box (light box, etc.) if metal and one attached to the framework of the fixture itself, and not to the white (neutral) wire(s).
Post us a diagram of what you now have.