What about gravity then? Gravity is what is theorised to have been slowing down the rate of expansion until around 6 billion years ago, when objects were far enough apart that the rate started to accelerate due to something we call dark energy.

In a static universe with shrinking matter, is gravity still somehow responsible for slowing the rate of shrinkage and if so, how? With an expanding universe, gravity defines how objects move relative to each other and at the same time can slow the rate of expansion between all objects. Surely gravity cannot be responsible for the slowing rate of shrinkage, so don't we need to introduce another new force? We still need the analogue of dark energy too, to explain the acceleration of the rate of shrinkage when it was initially decelerating.