It’s a fan film: the story is pointless and filled with various elements that make no sense (a walker within the city ? Is it the best weapon for this kind of environnement ?) just because they want to put a “SW skin” on it. But on the other hand it’s technically well made; it costed quite a lot so this is the minimum we can expect. It’s a well made fan film if you want. The actors… let’s say they try their best, which is not enough since the screenwriter didn’t do his job to develop correctly the characters.
A walker doesn’t make sense in any context. If you are going to criticize what is actually logical and congruent with other movies taking place in the same era, you might as well be fair. Walkers are slow and unstable, and when you have hover technology and speedy engines, why would you rely on quadrupedal machines? Heck, the ancient wheel is a more logical means of mobility for large machines. What advantage do walkers have? They are visually interesting for movie-goers. We are watching a fictional movie, and a little fan-service that also happens to make perfect military sense (the artillery was called in from an external area when the destruction of the facility on Scarif outweighed preserving the schematics for all those secret projects). If you’re going to be a party-pooper, might as well take it to its logical conclusions and point out how dumb walkers are in the first place.