“It is space-time itself that is expanding or accelerating.”
Sure, that’s fine, but I don’t think it solves the problem. There is still an acceleration to the expansion. Acceleration just doesn’t happen without some continuous application of force. If the big bang simply set spacetime to expanding, it would not be accelerating. Something must, right now, be continuously acting on spacetime to increase the velocity of the expansion. Not an event billions or trillions of years in the past.
I was more just pointing out that F=Ma doesn't apply to galaxies moving apart due to universal acceleration. ie, you wouldn't calculate the mass of a particular galaxy, then multiply it by the rate of the universe's acceleration in order to arrive at the mysterious "dark energy force" or whatever it is responsible for the acceleration.