Very rigid. One of the most important parts of a walk cycle is the movement of the hips and shoulders. In your walk, they just move up and down. They’re static. But in real life, they rotate right and left.
Also, your feet don’t bend or rotate either. The foot should bend at the toes. Keep working on this, though. I think you’ve started well.
The spine in your animation is always vertical. He really should be leaning into each step as he walks.
I’d recommend trying to get your hands on animation books by Preston J. Blair. They’re written for traditional animation but the rules he talks about in them are just as applicible to CGI. They also have lots and lots and LOTS of esamples and are definately a worthwhile investment.