The collective gravity of all matter in the universe does indeed cause a collective time dilation for objects within the universe. According to general relativity, the presence of mass and energy curves the fabric of spacetime, affecting the passage of time. This means that regions with more mass and energy will experience a slower passage of time compared to regions with less mass and energy.
On a cosmic scale, the distribution of matter and the overall expansion of the universe play a significant role in the collective time dilation. As the universe expands, the average density of matter decreases. In regions with lower matter density, such as the vast cosmic voids, the gravitational effects are relatively weaker, leading to a faster passage of time compared to regions with higher matter density, such as galaxy clusters.
However, it's important to note that the expansion of the universe itself does not directly cause time to run faster or slower. Rather, it is the gravitational effects of matter distribution and density that contribute to the overall time dilation.