Ok, I’ve been through this argument recently but lets see where this goes.
The problem I have always had with this argument is that it skips over the real meat of the question and jumps directly to “this being is what we call God”. The same sudden massive leap that Aquinas made. Now I’m happy to accept for the sake of argument that there was a prime mover (which I’ll refer to as PM for short). This PM is a “something” which happened first.
My question to you is whether you can fill in that gap and give the PM some of the qualities usually associated with the Christian God, instead of just saying “lets just call it God”. Lets start off with “personal being” how do you show that PM is really a personal being?
No Scholastic Philosopher in the last hundred years that I know of has made that claim - as much as they would have liked to be able to. Thomas did say he was offering five proofs for God’s existence. Judging from the reaction up to the present time the result is mixed and I say that as one who thinks he did succeed. However, the qualities of a First Unmoved Mover, A First Effecient Cause, Himself Uncaused, A Necessarialy Existent Being Who Cannot Not Be, Who causes all possible beings to exist, A Selfsubsistent Existent Being, the Cause of the existence of all other beings, A Final Cause directing the end of every other being are some of the qualities Christianity would ascribe to its God, who is definitely a loving, personal God.
Don’t judge Thomas too harshly. Remember, he lived in an age of faith. When he thought he had demonstrated the existence of God, I’m sure he took it for granted that everyone would recognize that god as the God of Christianity, the God of his Faith, the God of the Bible - a personal God. In his day there were no agnostics or athiests in the civilized world. There were Catholics, Jews, and Muslims. That was it. I don’t know how important this point is to you but that is the best that philosophy can do.
However, if you look at the universe around you, just taking it all in through your senses, just enjoying the beauty, the fantastic order and complexity, the amazing diversity of beings from zero ( so to speak) to a trillion and tens of trillions, the suitability of it all for the existence of humanity one feels compelled to believe in an all loving, personal God, the cause of it all. But then I am looking at it all as one who already believes. To me it seems impossible that some don’t, yet it is apparently true that some don’t, perhaps many.