My objection to Aria/Ezra was less to do with the morality aspect, more that I just found them really dull. Their scenes always seemed totally separate from all the other plots and I never thought they really knew what to with Ezra. They were always trying to throw various things at him - he comes from a rich family! He has a secret child! - but nothing ever stuck. I totally agree about Spencer/Toby. They never worked for me after the A reveal and IMO the actor playing Toby wasn't very good either. You're absolutely right that the writing was driven by shipper preferences, coming back to Aria/Ezra, this was really shown when they decided to hint that Ezra was A (which would have made the most sense out of all of the love interests who were A suspects) and then walked back on it because they didn't want the Aria/Ezra shippers to stop watching the show. Which was a real shame because both the actors seemed so excited about it in the interviews I saw.