I second Pistachio's sentiment - a lot of movement can be conveyed in limited frames. Adding more certainly
can help (when used appropriately), but you can still represent very wide motion without them. The brain will stitch together the missing pieces on its own.
I'm not able to make an edit right now unfortunately...but here are some (probably overused) examples of really successful low-frame animations:

- 3 frames, with one being used twice as a sort of "centered" frame

- 2 frames!
I don't have too much experience in animation, but I personally find it best to stick to a few keyframes first anyway. When those look good, I add more and more until it has the amount of fluidity I want. But if the keyframes don't convey motion well, additional frames will only make it more messy and difficult to work with.
In terms of concrete advise, and in hopes of not repeating what others have said, I think there needs to be more horizontal movement with the arms and legs. When we walk, our legs cross, but it currently looks like he's just picking them straight up and down. Even if it's a front-view of his walking (though he seems to be aimed to the left a bit?), I would expect that the receding leg moves far behind him - currently it stops just below him. And with a swagger, his arms and shoulders could really lean into each stride, going up to or past his belly. Right now they just go back and forth in a straight line.
It might be helpful to check for old games with front-view walk animations and see what their keyframes look like. Sorry I'm not able to offer an edit but I hope this helps!
