What's convenient about it? There was no coherent plan for Brexit. That's down to No.10, no matter which Conservative Prime Minister occupied it.
Parliament can only vote on what's put in front of them, and it took No.10 two years to deliver something that you yourself hated. And a change of PM to produce something that is functionally identical, except for leaving NI in the customs union.
Blaming it all on Theresa May isn't an excuse - if she didn't have the backing of Fox / Davis / Johnson, they should have resigned. But they didn't - so either they agreed with her plan, they were too incompetent to see the flaws, or they were too cowardly to resign. Please, pick one.