Often, when I run a tying class on trout flies I have to make the point that scruffy and buggy doesn't mean badly tied.
Practising and improving will allow the tier to make the decision about how rough-or not- the fly on their vice is going to be.
Obviously there are other advantages to being able to tie more than your shoe laces, not least consistency. If I tie 10 or 100 of the same pattern I want them all to look exactly the same as the first. Sizes and proportion should match so when I inevitably lose one or the fly is destroyed I can replace it with exactly the same thing that's been working.
DURABILITY; well tied flies last longer if you don't lose them. Fact. last November at IFFF Malaysia, a very famous fly tier gave me one of his signature flies, very neatly tied with perfect proportions. However, as soon as I touched it the thorax and wing rotated on the shank-a nice but badly made fly. Using gsp thread or UV resin is often touted as the way to durability. Last week I heard a podcast where an American commercial tier claimed that if you used uni thread for streamers they'd only last a fish or two - I'd make the counter claim that he shouldn't be a commercial tier. There's no substitute for proper technique and tying materials tightly and properly to the hook.
Lastly, I think catching the angler is important in a way. When I open my nymph box and the rows of Walt's Worms, perdigons etc. are sitting there like a bunch of clones, I take away a decision - I don't have to look for a good copy of my chosen pattern. And I fish better, because I am confident in the fly which lets me focus on technique.
Practise, get better and doing the best you can at the vice, on the water or just in general.