I watched a few episodes because it made a list of 'streaming shows that were cancelled too early'. I hadn't even heard of it before.

Well, it's just not very good. It covers familiar territory going back at least as far as Time Tunnel. I had an expectation that in the 21st century I'd be seeing some cutting edge FX and that the stories would be more nuanced than the simple dichotomies of a previous era. No such luck. This series looks dated. If I had been told it had been made in 1990 I would have believed it. And really, if one is going to be taken the well worn path, an injection of something new and interesting is essential.

And the characters are flat and uninteresting. With Quantum Leap one had engaging characters that we cared about. And every week we had 'minor' characters we were given reasons to invest in. But with Timeless, what are we to make of the lead character's missing sister? We don't know either of these people. We don't know what has happened. Is this like Sliders where these people still exist but in another timeline? It's a puzzle, but it never becomes personal in the same way.

It's been done too many times before, with better writing and better characters.