I got it expecting to hate it, but as I kept playing, I found myself legitimately enjoying it. Not begrudgingly enjoying it, not enjoying it outside of one or two small details, but actually being engaged in the story and gameplay. Which leads me to wondering why people had a problem with this game in the first place again?
For what it is worth. It is implied that this takes place in the Agents of Mayhem timline as you find the 3rd Street Saints symbol in an abandoned church, Johnny Gat is mentioned in the description of one of the weapons as being a famous person, and you can buy an Agents of Mayhem T Shirt.
So the old characters not being present is explained.