There are some disagreements among skeptics. There are some threads of thinking, however, that are very popular.
As a disclaimer, I must admit those who doubt do not know there is no god nor whether there was a Jesus. On other issues there is more confidence. There is evidence about the kind of person Jesus was, if there was such a person, and what and why certain events happened. These are at odds with the prevailing conventional wisdom in Christianity generally.
These ideas are discussed in the links below. Their origin goes back into antiquity.
I’m well aware there are scholars who study this stuff and come to different conclusions. The disagreements have been there for 2000 years. What I would call the basic critique of scoffers are these:
The Jesus character was not about simply loving people, but was apocaplytic and politically engaged.
Jesus did not see himself as the Devine. This was assigned to him by others later. He saw himself as the son of man.
Jesus was not born in Betheham.
Jesus probably was not literate–could not write.
Jesus died because he came to be seen as a King on earth, a competitor of a current King, not as a King in heaven. He died for a common violation of political norms of that time.
Jesus was not about marketing Christianity to the pagans. It was Paul who came up with that idea. The Bible shows many followers of Jesus did not like Paul’s idea.