I guess we just have a different outlook on diving. If you agree to be a team you are a team. In this case the experienced divers would be looking out for the OP on his first dive. If they didn't want to team up they just should have just said no thanks.
Yeah, basically I agree, but I think that there are nuances here. I personally don't like the idea of a new diver surfacing alone, as I said upthread.
That having been said, if you feel that the experienced divers who let him tag along should not have done that unless they were willing to do a short (15 minute?) dive instead of what they had planned and paid for, then the right thing to do would have been for them to just say no.
Which would have meant that after all of this preparation, cost and effort, the OP would just be sitting on the boat with his rented gear, watching bubbles. All because the shop had told him that someoene would dive with him. And for most people in that situation, that would be the end of local diving for them.
It's not a great situation, but I have definitely been there many times and it sounds like everyone tried to make the best of it. Maybe a crew member could have been hired to be a guide or something? Depends on who is available and willing, right?
Not an easy situation, and the errors started long before the boat left the dock. But a good learning experience, for both the OP and for other new divers reading this thread...